Writing programs is easy. You just need to do between 1-20 sets of 1-100 reps per muscle group at between 5-120% of your 1RM and rest for 1-300 minutes between sets. It’s science. This is obviously an exaggeration of what is written in most textbooks, but most textbooks provide general guidelines but fail to explain how to individualize those numbers for your client.
Source: Fitness Life Nutrition