ok, now that I have more time...
I keep my party spread out in a fight. It reduces the chances/number of chars that get affected by area effect spells.
I use the autopause for practically everything, and I turn the party AI off. Yeah, it slows down the game, but it makes it infinitely easier to control the party (especially my spellcasters). In BG1, not a single enemy spellcaster (except when there was more than one like in the Red Wizard area) ever got off a spell because I had one of my mages time his magic missles just right. And before anyone says that this is a cheese tactic, it really isn't. Put it in roleplaying terms, if you see an enemy spellcaster talking like they're about to cast a spell, you want to stop him and stop him fast, which is why MM is so handy. There were actually a couple instances when this didn't work, but that was only when the enemy caster was casting spells with a casting time of 1 (like MM). Still a good strat, IMO.
Keep only one Tank. I only have one tank in my part. Granted, I have two backups (Jah, Vic/whoever), but I designate only one tank and give him the best gear. He goes into a battle first, and because he's got all the good gear, he gets hit really little.
With this in mind, I always have at least two mages. I'm going through BG1 with no cleric (I have Jah for healing), and me and Dyn as mages. They can -really- buff your party, as well as deals some serious damage themselves. The only problem with this is that later in the game it seems everyone has 500% magic resists and saving throws of -50, but then you just use lower resist and greater malison (though it wastes a couple rounds).
Just as Nish works well against mages, Morwhatever's sword works well against pretty much anything with a non-magical attack.
As for trolls, keep some fire or acid arrows just in case, but a lot of times, Minsc (with a sweet 2H sword) would just gib them. The trick is for him to get a good hit in when their hps are really low. This shouldn't be a primary strategy, just something to keep in mind.
There was a huge debate a while back about whether or not Imoen is a good thief. She isn't naturally, but she can be (I realized this recently). There's lots of gear in the game that seriously jacks up a thieve's stats in certain areas. Just have her keep the gear on hand, and equip it when you need to.
Like I said before, the best legit char for me is a Mage I brought in from BG1 to be a wild mage. The main reason why I did this is so I could Tome his INT to 19 and not have to worry about using potions of genius, or picking spells to not scroll into the spellbook and all that rot. Besides, nobody else can make it rain cows...and that is what the BG series is all about.
