Well, here's what i do, hope it suits your game play. It differs from the aggressive mage most do, it seems.
- invisibility is a must. i spend most of my time invisible in QA...
- don't attack with ranged weapons if fighters are doing fine, you'll only attract attention, and you value added attack is very low,
- brew potions: lots of easy money to be had this way.... and it helps others.
- there's a difference between low levl and higher lvl play:
- low lvl, take what spells you like, and summons works fine
Higher lvl (more than 5), here's what i do:
- i play a full supportive sorceror: no attack spells (for the same reason as above), and mostly summoning items (you can find a lot in the game, summons don't cancel invisibility, but are used mainly to ease the strain on fighters, not to inflict good damage),
- always protect yourself (especially elemental protection, and when you can, stoneskin or blur when you see it's going to get rough)
- once you know what you're up against (but don't meta game before the quest !), cast the right protection spell (blur for small enemies, elemental protection everytime, mind wards, etc...)
- get spells your team wants and that last more than a few rounds: strength & dext enhance, magic weapon, protections, wards, dispels... (remember: magic weapon+strength= about +3 bonus, on 1d8 weapon, that's 40% damage you increase, and it last long !)
- stay away from the fight (risk of area damage spells which will kill you straight off, or being spotted: invisibility only helps so much...)
- be ready to heal others with items or herbs: that's your second job once your supportive spells are active (or gone !)
- i try not to bother about "picking a good team": first, choice may be limited, second, i try to get new PCs/players to play, third, if you don't engage in melee, you'll survive a lot whatever the team. I've been the only survivor on a few quests, and stayed alive to bring rescue team or to take the bodies to some safe spot
- if you really want to cast those offensive spells (which can be really deadly), take precautions such as casting hasty retreat just before, or invisibility just after... and remember area-spells will likely hit your team, so be careful...
- magic missile is very efficient: no ST, good damage, you can cast a lot, long range (safety rules !)... Very handy when the fighters just can't hit that big boss !
- if you can, hire a bodygard (though i believe easing the strain at the front will be much more effective, so don't take a fighter or rogue away from the combat scene just because you feel chilly...) In this matter, rp is very important to make loyal friends...
Don't expect to attack (spell/ranged) without being targeted... and since your AC and HP are low, once you're targettted, your chances of survival are low (especially higher lvl enemies)
You're no frontliner, nor secondary line. You're full support. You could cast your spells in town and stay there if they lasted long enough or weren't dispelled!
There's a huge difference if you dual-class with a fighter sort, because then you're expected to fight... Pure mages just don't fight... Whatesmore, when you hit pure classe lvl 6 or 7, you get veeery nice spells (stoneskin, improved invisibility...), which you'll never get if you're 3/3 or 4/4...
Bottom line: pure mages must be cowa... hu, cautious ! I've only found one PC to ever blame me for being hu... very cautious (lol !: "why aren't you fighting, girl !Take your staff and fight !" -against trolls !)