a few questions if you dont mind
totally depends on the individual, everyone should know what they are capable of and how much weight they can nail. but i will answer these for what i do.
what rep range do you work in? is it different for compound vs isolation exercises?
I typically do 6 reps for compound movements and gradually increase weight per set, then once i reach X amount of weight I nail it for 3 sets to build consistency with 3-5 reps heavy. then with isolation i tend to go till failure on each set. i like to hit the red muscle fibers with these, so a lot of reps at lower weight.
what % of your max are you using for the sets?
with compound lifts i warmup and gradually increase the weight. i don't max out very often, maybe once every 3 weeks.
do you use the same weight for all the sets?
generally no unless I am doing centuries. for example my last push day.. i started out with flat bench. put on 135.. warmed up.. then put on 225 and did it 6 times (did not go to failure as i dont want to burn myself out) then jumped to 245.. did it 6 times.. then 275 4X.. then 305 3X for 3 sets. then i went to 315 and did 2X. then i went to incline and did 225 for 3 sets till failure. next workout i might just do 225 12 reps for 5 sets. or if i want to max out i will do 3 reps at lighter weight then throw on 330 or 335 and try to nail it a couple times. then go on to something else.. so i mix things up. really when i warmup i get a good feel for if my body feels like it wants to push heavy and low rep, or lighter and high rep. same goes for leg days doing squats or deads. same goes for pull days. from a pure bodybuilding standpoint you definately should aim to hit your white and red muscle fibers probably 35-65. powerlifters should go 75-25