For example, lets say you are currently doing 3 sets of 8-12 reps on bench press with 200lbs but you can't get passed it. Modify your workout as follows:
Week1: 180lbs, 3 sets 8-12 reps.
Week2: 185lbs, 3 sets 8-12 reps.
Week3: 190lbs, 3 sets 8-12 reps.
Week4: 195lbs, 3 sets 8-12 reps.
Week5...