Im talking total beginners and people who have injuries or issues that could become injuries. These people have no idea about muscle balance, progression, flexibility, metabolism, or how to do exercises properly (even basic ones like squats, deadlifts, etc.)
I teach about muscle activation and how to listen to their body, what does what, how to do a movement properly, how to miss a lift, breathing, how to apply it outside of the gym, and if they have fat or muscle goals, how to diet given their circumstances. If I have an athlete, we do things to bring up their weaknesses and they still learn the stuff above, but also how to apply it in their sport. You can see TP4U's thread about his bro where I commented there. I also do trigger point work and some myofascial release for people who have overuse injuries or mobility and/or flexibility hindrances.
If I were training someone for SM, and they needed help on improving a lift (say log press) I would check out their positioning and point out the weak links. Then explain how to stay in proper positions and exercises that will help. I may even video their lift so they can see.
Ive had several certifications over the years such as NSCA and ACE. I also have a coaching certification for Olympic Lifting via USAW. I dont have a degree in this stuff, but that hasnt kept me from learning about physical therapy, rehabilitation, myofascial release, etc.
Yes I will do diets for people and help people diet into certain weight classes for performance purposes. I make them for each client based on their work schedule, goal, training frequency, etc. and regular feedback.