I was in a party which exercised good discipline and tactical thinking, that is right up to the point where we TPK'ed. Usually my character, a Fighter-Ranger (headed towards Dwarven Defender), organized the tactics, which was fitting as we were in a dungeon (the World's Largest, in fact) and he was hired for his tunnel/underdark guide skills. Tactics revolved around trying to fight through doorways with my Guisarme, anything that crossed the threshold gets whammied by the monk and rogue/wizard flankers with the priest healing whoever got hurt.
Replacement party hasn't shown much tactical acumen yet. The halves of the party have just met (been thrown together by circumstances); no one has stepped up to be the leader and I won't with my new Bar2-Ftr2-Sor1 (next level: Dragon Disciple!) as he has no schooling in such matters in his background. The extent of his tactics are, "let me trip the guy and then we beat the snot out of them while they're on the ground. Ha ha ha!" If he has a chance before the battle starts to prepare, he'll work himself into a frenzy which often 'triggers' an 'inexplicable' growth in size (casts Enlarge Person). Should I fail the spell failure due to armor, then it becomes a standard rage instead. I've broken out the True Strike-Power Attack combo a few times as well.
The Dwarf likes to bust out his own Enlarge Person and Bull's strengths, usually on himself, as he's a war priest. If the tunnel is narrow and he can't easily get in position, he'll stay back and buff/heal the front line. Bar-Rogue is usually raging and will try to flank if he doesn't think he'll get mobbed by the rest of the baddies. Wizard seems to like Flaming Sphere and Magic missile.
Another party, currently on hiatus, suffers from the "either we wipe the enemy out without a sweat or we are pushed to verge of annihilation" problem. We have a halfling Rogue(2-reformed)-Paladin(11) on riding dog, an elven fighter 12 (not optimized at all), and my Ranger(1)-Priest (12 Fharlagn luck/travel) archer who ends up as the jack-of-all-trades for the party.
Ideally, I'm flying, divine favored, and the paladin has plenty of room to charge. Flame strikes and recitation are usually the only offensive spells I bother to throw. If I'm forced to move in a round (perhaps to get within 30' or get line of sight), I'll take the opportunity to cast spiritual hammer instead of firing one measley arrow. That's about the extent of our tactics (Paladin: "They detect as evil? CHARGE!!!) Anytime the paladin can't charge around freely, we struggle pretty hard. I was one of the primary damage dealers of the party (archers don't have to waste partials chasing the bad guys around), but near the end it seemed like I spent all my rounds busting out the random spells to counter the effects of the enemy (break enchanments, dispel magics, heals and cures) to keep my two compatriots alive and kicking. One nice thing, is that when it got bad, I was usually able to dimension door us all to safety.