Guide written by Hermit Boy on the DiabloII.Net Single Player Forums.
The Sorc is probably the class that least needs a guide, but I figured someone here would get some use out of it, so I decided to write one. Keep in mind this is for Single Players and is focused on getting a sorceress to Matriarch status.
Right off the bat I want to point out Venomous Vixen's guide which is the best resource I have seen. It is at www.d2source.com/LoD
Strength This is only important for equiping items. It is up to you what items you want to get to but here are some good goals. I would recommend having 60 at the least. This allows you to wear a plated belt which is the only normal belt with 4 rows, although you could wait to get an exceptional demonhide or sharkskin belt which has much lower reqs. 60 also allows you to use Frostburn gauntlets if are lucky enough to find them. Go to 78 or 83 if you want to wear Naj's or Tal Rasha's armor respectively. Archon plate, elite light plate, is 103 which is probably the most any sorc would need. If you want a 4 socket sheild the minimum strength is 184 so forget about that.
Dexterity This is all but useless for a sorc so don't put in any.
Energy This is a tough one because it depends largely on your skills. You definately want a lot so put at least 2-3 per level here until you are compfortable. You want to put enough here that you can support your spells, but there is definately such a thing as too much energy.
Vitality As with all classes, all spare points go here.
Mana I have found that anywhere from 600-1000 mana is sufficient. With this amount, and a decent mana recovery rate, you will rarely have mana problems. Mana pots are easy to find and will only be needed occasionally. If you run out after a large fight, you probably want to just rest for 10-20 seconds and you will be full again.
Life You need a large amount here. Although you will try hard not to get hit, you will get hit often. The sorc has only her merc to tank, no minions, so you will be targeted often. A good amount to shoot for is around 500 or more. With this amount of life, you will almost never have to worry about one hit kills. You should never get hit more than once or twice, because you can teleport away if you need to. More life is always better though.
Venomous Vixen's guide has a great indepth description of every skill. Check out that site if you want detailed info, but I will give some short descriptions, especially how it pertains to SP.
Warmth This increases your mana regeneration rate. Get this skill ASAP since it will help you early on, but it is less effective later. Some people see how much it helps early on and pump too many points into this skill, then find out later that they have more mana regeneration than they need. I recommend putting around 5 points here early on. 5 points will help you a lot, and that will increase as you find +skills items. Around 10 is the ultimate goal for this skill. Again it depends on the skills you are using. Later in the game though, it is usually better to increase your max mana then increase your mana regeneration rate.
Fire Wall The all powerful fire spell. This is probably the most powerful spell in the game. It has insane fire damage. The main problem is hiting monsters with it. Usually it is hard to convince them to stand in the fire, so they end up getting hit once or twice by the wall. If you use fire wall, you will need to develop some strategies to keep monsters in the fire longer. Here are a couple of ideas.
Meteor This does a good amount of fire damage, but has a long delay from the time that you cast it to the time that it hits. In SP you don't have other people to tank for you and hold monsters still. Also you have no minions, and only your merc to tank, so it is rarely possible to hold monsters still long enough to hit them with it. This means that you need to time it and anticipate where the monsters are going to be. This is very tricky, and sometimes dangerous. In SP there are many better options than Meteor.
Hydra This does good damage, but suffers a little from delay. The spell timer on this is 2 seconds, plus the hydra does not start shooting until 1 second after you cast it. This means that it is hard to use this as a primary skill. It is a great secondary skill though since the hydra's attack by themselves without any help from you other than the initial casting.
Fire Mastery If you use fire skills a lot, you will definately want to put a lot of points here. In most cases however, you are best served to make the attack skill like firewall or hydra before putting points into FM. However, you want to put at least 1 point here as soon as possible to take advantage of the large initial bonus and +skills items.
The other fire skills are nice and fun, but really are not worth investing in.
Charged Bolt This can be used as a primary attack skill. However, if you are going to do that it is critical to get this skill level as high as possible. +skill items are more important for this skill than most others. You will also need lots of fast cast items. It can also drain mana very fast. You kill with this spell by the sheer amount of tiny bolts that are flying all over the screen. Individually they don't do much damage, but collectively it does a good amount of damage which means that you may need to get closer to monsters than you would like in order to hit them with more bolts.
Static Field A very nice spell. It is limited now as to how much it can lower the monters life in Nightmare and Hell. I found that in Hell you usually only need to cast it 3 or 4 times before it does not do anything anymore. Firing it 3 times before every battle is not too mana intensive, takes little time, and helps a lot.
I recommend getting to around lvl 10 which is where it will hit most things on the screen. With +skills items you probably only need to invest around 5 or 6 skill points.
Telekinesis Mostly worthless in SP, but needed as a prereq.
Teleport Absolutely needed, but only 1 point is necessary. Cast is to get out of harms way and any other time you feel like it. One nice thing is that when you cast it your merc will teleport to your side. I will sometimes teleport right next to myself just to get my merc near me.
Nova Useful as a primary attack. This does decent damage, but is very mana intensive and needs some fast cast items. Also the radius is fixed and you need to get a bit closer to monsters than you would sometimes like.
Chain Lightning This is also good as a primary attack. While this does not have a timer, it does take a long time to cast. fast cast items do not help with this spell, but Increase attack speed items do. If this is your primary attack spell, IAS items are a must. It is not too mana intensive and hits pretty well. This is best when shooting into groups. If you are using it to attack a single monster, it usually does not do nearly as well.
Energy Shield This is both a good and bad spell. It absorbs damage for you which keeps you alive, but it also can drain your mana quite fast. With ES activated, twice the damage that it blocks is taken from your mana. For example, if ES saves your from taking 20 damage, 40 mana will be subtracted. If you are somewhere where you are taking a lot of damage, this can keep you alive, but you may run out of mana before you realize what is happening. The higher the skill the more damage you do not take, but the more mana you lose. I recommend putting 1 point only and letting your +skills boost that a bit more.
Thunder Storm This is one of my personal favorites. At low levels it is not very good, but as you increase this skill and LM, you will get insane amounts of damage from it. For example at slvl 15 it can do 10,716-18240 damage over 144 seconds. And that is without LM. The only problem is that the damage it does is over time, so it may not be a good primary attack. This is without a doubt the best damaging support spell there is. I use it as my only lightning attack and it works fairly well. I have it turned on all the time and it will sometimes kill monsters before I know they are there.
Lightning Mastery This increases lightning damage. As a general rule, you want to increase this at about the same level that you increase the attack spell. Maybe a bit slower.
Frozen Armor This gives you a bonus to DR which is good in normal, but does very little in Hell. It will also freeze monsters when they hit you, giving you a chance to escape. However, in Hell the freeze time is penalized so much that the monster is usually unfrozen before you recover from the hit. Overall, this works well early on in the game, but is almost useless in Hell.
Shiver Armor Much like Frozen armor, it is good in normal, but becomes almost useless in hell.
Chilling Armor Again, this can be good in normal, but virtually useless in hell. This retaliates against ranged attackers instead of melee attackers.
Frost Nova Very nice early on, but inferior to Frozen Orb in every way. Do not invest in it.
Ice Blast This freezes monsters and has a somewhat decent freeze time. This is better used as a way to freeze monsters inside your FW then actually doing damage to them.
Glacial Spike Much like Ice blast but has an area of effect and freezes them for a shorter amount of time. Use this in combination with FW.
Blizzard This can do decent damage, but will sometimes miss the monsters. Since your only tank is your merc, this is not always a good spell, since with the timer you cannot have more than 2 active at the same time. This would be better in MP games where you can have more people to tank for you.
Frozen Orb This is my favorite spell for a number of reasons. Even though it has a timer, you can cast the second one before the first one is done. It does very good damage and has a very good chill time, even in hell. I used this as my primary attack all the way through hell and it worked very well for me. It is a little expensive manawise, but at slvl 20 and 900 mana, I rarely ran out. The area of effect is very good too, so you will usually have most monsters on the screen chilled, which also helps your merc immensly.
Cold Mastery Many people do not know how this works. See venomous vixens guide for a full description of it. Basically it only effects monsters that have cold resistance. It has no effect on monsters with Immunity or no resistance at all. CM reduces the resistance of monsters that have a resistance, but it will not reduce their resistance below 0%, or even to 0%. In hell, most monsters that had cold resistance in normal or NM, are immune, so CM does nothing. There are still a few monsters in hell that have cold resistance, but not many. 1 point invested is sufficient, then that should got up to 5 or more with +skill items. That is all you need to be effective.
In SP it would not be a good idea to focus in 1 tree only. 2 trees would be viable since you would only run into double immunes with some bosses. The best thing to do in SP is to invest in all 3 trees. Invest heavily in your primary tree and a backup tree. Then in the third tree you only need to invest enough to kill the few double immunes you will encounter.
Since this is SP I will assume that you may not be able to trade or mule, and therefore may have to just use what you find. It does not do a lot of good to aspire to a certain unique or set item.
Plus to skills is probably the most important thing to look for. Especially since you will probably be investing in all 3 trees and may not have enough skill points to max what you want to.
Plus to Mana is probably the second best thing to look for. It also works to increase your mana regeneration rate but +Mana items increase your overall mana which in turn increases your mana regeneration rate, whereas mana regeneration items only increase mana regeneration and not max mana. Also you can get damage taken goes to mana items to offset the mana lost from ES. +mana per kill is also nice.
Fast walk\run speed helps you avoid monsters.
I would strongly recomment a shield and one handed weapon unless you find a fantastic 2 handed weapon. With a 1 handed weapon and sheild you have blocking, better resistances, and twice the handheld items that can give you magic attributes.
Circlets are very good because you can get good +skills on them. Same goes for amulets. Usually it is not hard to gamble for these items, especially because you will not be using much money to repair items.
Teleport often to stay away from monsters. This also causes your merc to teleport next to you to protect you.
Baal and the Succubi have a Magic Iron maiden curse that is very bad for a Sorc. When you cast a spell, you will take damage in the amount of the mana that you cast. You cannot die directly from it, but it can lower your life awfully fast. The trick is that they only use this curse on you if you have more mana than life. It may be worth switching gear a little when you fight these monsters. For example, I change my +mana rings to +life rings to put my life about mana, and then I don't worry about that curse.
You really need a merc that can tank for you since you have no minions. An act 3 merc would be almost totally useless and an Act 1 merc would be only a little better.
Act 5 barbs work well and are probably better than an Act 2 merc. The only Act 2 mercs you would want would be either a defiance merc or Holy Freeze merc if you do not use your cold spells much. A prayer merc might be nice also, but I doubt they would heal you fast enough to do much good.