i second all of what roy said, plus:
1) you often don't need much fold equity for a turn raise to be a good play with a modest hand. 20% fe + fd + gutter is usually a good image play that rarely sees you as a big equity dog. the strength of the fd obviously depends on villain.
2) expanding on what roy said (2nd paragraph), i think good turn play depends on how villain(s) will play the river. if they're passive, weak-tight (esp. if it's telegraph check-fold), or blufftards who'll pay off when you hit, often times calling and seeing the river is the optimal play. this concept is very much lost on most of the 2p2ers who seek out small edges (incl. fold equity) at every opportunity instead of taking larger edges on later streets.
3) check-raising is often very different than raising, imo. i will often check-raise relatively light on the turn (e.g., bare nfd) if i think that villain is floating/sponging my flop bets too much. i also do this with big made hands, so it really slows the floaters down since they usually figure out that i have a monster or equity. this same concept applies to people who donk bet the turn regularly on steals or bare draws -- that is, i'll raise ip relatively light just to try to keep them in line.
4) i personally find the modest draw play (in roy's terms) more interesting when considering a second barrel on the turn (ip or oop). i think you often have more fold equity on a bet than when you're raising -- that is, a bet is more often a made hand than a check, so you have a better idea of where you're at (although it's not always clear).