My entire daily program is designed and updated (and monitored - "Whatcha do yesterday?") by my genius trainer. I do what I am told by him. As Mrs. BD says, he is the only person I obey besides God.
My current program is 2 days of heavy weights with trainer, one day of accessory weights mostly by myself, one or two conditioning classes at the gym (tough and fun in a sick way) or replace one of those with an hour of my own calisthenics, one day of endurance cardio and one day of misc HIIT cardio. Everything is progressing nicely but slowly of course. I'm not 18 anymore.
Speaking of which, have you noticed so many people checking their iphones at the gym? They aren't looking at texts. They have their exercise plans du jour on their phones, and are checking what their next circuit should be. Luddite that I am, I write them on paper.
But to my issue of 5 vs 3 sets of resistance work.
My approach with the powerlifts is one light warm-up set of 5-8 reps, then 5 working sets of 5-8 reps of increasingly heavy weights. 5 is my favorite number, but some days my boss pisses me off by making me do 8s. When we go near my max, say, with deads or barbell squats, only 3 reps. My modest one-rep goal is 300 for deads. I am not a big strong dude.
With accessory resistance work which I do on my own once weekly, I generally do one warm-up and 3 working sets. It's partly a matter of time (because 60-90 seconds rests between sets), and to fit in everything on my list with 60-75 minutes. It's rare than I can fit in everything on my plan.
What sorts of things do I do on my accessory weights days? It's below the fold -
Pullups alternating with pushups, leg press or goblet squats, calf presses on the leg press machine, kettlebell farmer walks, curls, Roman chair leg lifts, kettlebell step ups, inclined dumbell chest presses, kettlebell lunges, kettlebell swings, inclined pulls on those strap things, etc.
Usually I throw in heavy ball squat throws and jump rope as active recoveries. Often I do 5 sets of pullups because I am working on a specific goal there. Golly, they are difficult for a middle aged guy. Skinny women seem great with them.
I am fortunate in having many hobbies and interests - too many to keep up with - but my daily workouts are probably my most valuable hobby. My happy routine: Grab a Dunkin at 4:30 AM and get to the gym by 5 ready to rock and roll. I should mention that daily workouts are great for people to do with a spouse or girl/boyfriend. Another thing to do together, and mutually-inspiring.