All of my clients have a written workout every time I meet with them. I write what they do every session. I also keep a seperate measurement chart (weight, bodyfat, measurements, etc) which I update periodically (weight more frequently as it only takes 30 seconds). They also have a written plan that outlines where they are, where they want to go and the steps I am going to progress them through (I use NASM’s OPT model).
I am training my trainers to use this model also.
The written records allow us to easily pick up a file and give any cleint a great workout at the drop of a hat should another trainer have to cover. It also is great so you can show your client their progress!