I do 30,45, or 60 minute sessions. How long we go depends on what they need. As far as how I design them, I have a few different template style systems I use depending on the clients needs. Alwyn Cosgrove has a fantastic article at
EliteFTS - Powerlifting and Strength Training Products and Knowledge for Lifters, Athletes, Coaches, and Trainers called the 7 keys to athletic success (I know it starts with 7 keys, the rest might be wrong) that outlines his template. I would also highly recommend that you check out
Strength Coach.com | Strength and Conditioning | Sports Training. Its Mike Boyles fee based website but he just put up an article with his template that he uses with his athletes. Its another fantastic article. You can do a 2 week trial of the site for $1.
Danny