To take it a step past what Hugh was getting at, it's not necessarily about the exercise itself unless you're talking about a very specific lift (like the board press or yoke walk). Most exercises are used by everyone - bodybuilders bench, powerlifters do dumbbell rows, Olympic lifters back squat, strongmen front squat, etc.
It's more about what you're training for. The easiest catch-all forums are Beginners (pretty self-explanatory, good for all folks starting out) and Bigger, Stronger, Leaner (again, general and what most people are actually looking for in the gym).
If you're training for specific strength sport or physique sport, then it's a sure-bet to post in one of the relevant forums. Worst case scenario, post it where ever and a Mod will re-locate it if needed.