1. If your goal is 8-12 reps for an exercise and you make it to 12 reps with relative ease, don't stop at 12 -- try a few more until you go to momentary muscle failure!
2. If you meet or exceed your rep goal, add on the least amount of weight you can on your next workout for that exercise. For example -- let's say you did 12 reps of 100lbs on the bench press. For your next workout, add a 2.5lb plate to each side for 105lbs. You may only do 8 reps with the new weight, but stay at 105lbs until you meet or exceed 12 reps. Then move up again.
3. It's impossible to remember all the sets, reps, weights, and exercises of every workout. Log all your workouts on your phone so you know what you have to beat the next time.
Progressing in reps and/or weights with each workout is the foundation of great results! The sad news? It's seldom understood or done properly. Follow the above steps and it'll keep you moving in the right direction with your workouts. I promise!