I rate each set with an effort, between 1 & 10.
My first set will be about 50% of my projected last set, 10 reps. The effort here should be 6-7.
My second set will be 75-90% of my last set, 10 reps. The effort here should be 8 1/2 - 9 1/2. I should only be able to get one or 2 more reps if I tried.
My last set will be from 3-6 reps, not necessarily to failure, but so I couldn't do one more. Sometimes I have to cheat a little on my last rep. The effort here should be 10ish.
I workout in my basement. I can't stand working out with others, so I built a cheap squat rack with a high pulley. I also can't afford to hurt myself, so I maybe don't push quite as hard as I could.