2ndhandsmoke, does make some basic good points, on tot selection when fighting.
This is my basic game plan on dropping tot's myself. Any melee class, Earth bind, which pretty much means Enh Sham's, war's, rogues, etc.
On rogues, Poison Tot...most rogues I've encountered on BG's don't use their anti-caster poisons, and tend opt for the crippling usually, either way...taking away that aspect of their fighting can prove rather annoying to them, which is great for us :)
As far as wind tot's goes...this is a toss up. Unless its a for sure caster (caster=Grounding tot of course), I usually throw down a nature resist (rogue, druid, sham), or a GoA. GoA I only endorse if your enh spec...as others spec's, there's not much that can help you in the Air tot catagory much.
For Fire tot's, I'm usually putting down searing. If its a Hunter and I run into their snake trap, then I throw down magma (best anti snake trap thing in the game, IMO). Occationally I might use a fire nova, just to change it up (or if I need some quick burst dmg to finish them off.
Note for tot's. Tot's are "nice" but againt "good" players, especially ones that know a sham's bag of tricks...totems can be BAD! Since tot's basiclly have NO HP, and can be 1 shotted, throwing down tot's can and will be taken out QUICKLY by ppl that are hip to a sham, and know what each tot can do for us. This will basically lead to running us OOM, which isn't hard to do thanks to our lack of MP pool depth, at which point regardless of spec...your SOL! Endurance matchs aren't something where good at. I sometimes fake some ppl out with a fire nova tot, after a searing tot or vice versa, due to their activation times and durations.