My tactics are generally to gather all the information that I can, plan ahead (with an eye towards special items that might help with the current mission), carry all the useful gear that I can, including a host of missile weapons, coordinate spells (assuming I can get the party to), try to get them all to the same mobility rate, at least overland (this never works, as there's always someone with a mule and/or riding dog).
In combat, I always use missile weapons, first, if at all possible. I will use stealth and cover as best I can, and avoid melee. I also make frequent use of Spot & Listen to detect incoming threats, and often win Initiative, then hold fire until just before my next action, or until I see a spellslinger opening up (and then I try to ruin their spells). I carry a host of weapons, including all the "special" ones in the PHB, so I can take out most things. I also have light, blunt, piercing, and slashing weapons, so if I know what the DRs are, I can usually get around them. I can also cast non-magical (Alchemists') fire-balls, (Tanglefoot Bag) webs, acid sprays, deafness (thunderstones), as well as silver and cold iron arrows.
I'm also the party generalist. While there are plenty of things I stink at, there's almost nothing non-magical that I can't at least take a crack at, and if the DC's below 25, I can probably pull it off (at least once in a while). I also collect Synergy & Circumstance Bonuses, and carry the gear to improve our chances at doing whatever... While the rest of the party is trying to react to the sudden darkness caused by the Antimagic Field, I'm the one pulling out the glowrod and restoring light.
I'm also the guy with the three tinderboxes and two magnifying glasses on him, who also knows how to start a fire with just his knife/handaxe and bow, too. I'm also the go-to guy when the Rogue breaks his masterwork thieves' tools, and no one else thought to buy a backup. I'm also the only guy at full strength, instead of weakened and starving, when the GM starts us off after two weeks in the desert with no food or water available... I'm also the one who supplies the rest of the party with water. I'm also the guy who, when the Rogue breaks MY picks, AGAIN, produces a needle and suggests he finish the job with a -2 Circumstance Penalty, instead of just dooming us.
"Young soldiers argue tactics. Old soldiers argue strategy." I tend towards strategy, as much as possible, but then try to apply the assets tactically. Sometimes, I even pull it off. In any case, if it's smaller than a battering ram, I can probably either produce one out of my backpack, or quickly make one out of materials commonly available in the woodlands.
I'm also the guy "slowing things down" by investigating everything, collecting the clues, buying the asbestos (or better yet, nomex) gauntlets, and frequently, reaching into the fire to pull our fat out of it!
Unfortunately, I'm also generally the one trying to "herd cats" and coordinate the PCs, set up tactics, get the party to work as a team, etc., and generally seeing the same sorts of tactics as most of the other posters, here... Basically, none!
As for spells, I usually have none. On the rare occasions where I have a magic item that allows me to cast one, I have found the GMs who gave them to me rather unwilling to let me use them intelligently. I end up selling them for cash to get "more useful" stuff, instead. When I use one of my few spells/day, it's just a Speak With Animals to gather information or request aid, or Entangling a foe and sniping at them.
I try to hide and snipe, and/or use concealment/cover. I can melee, when necessary, but like a Rogue, without surprise, I will usually get hammered. On the good side, though, I can use a wand of Cure...
Basically, since I find party cooperation negligible, I tend to do what I can, encourage the others to work together (coordinate spells, all of that), and just do what I can and try not to worry about what I can't.