To me the most important consideration is working to temporary muscle failure by the 12-15th rep. Good form, good posture are assumed. Without temporary failure the IIb fibers aren't activated.
Good answers. Regardless of body weight/size the determination of reps/sets to temporary failure depends an your client's goals. Temporary muscle failure is the key since that indicates that the challenge has reached to the IIb fibers.
How do I put my bike in my baggage?! I recognize that the responses focused on food. Definitely can be a challenge. Everywhere I've ever been there have always been good food choices. When in Rome........Just be as active as you can be in your environment.
Good answers. Stretching lightly before a workout helps prepare the tissues for the overload. Stretching after, when the temperature in the environment of the tissues is up, helps prepare the tissues for increases in ROM.
Interesting way to market one's program. Abs! All are great exercises that will overload the various muscles that comprise the abs. One that doesn't get a lot of attention--what I call reverse trunk curls. Supine, hips at 90 degrees flexion. No movement at hips or knees, posteriorly tilt pelvi...
The answers are all great. Neither one is necessarily the better type of training. They are just different. Sets target the muscle group(s) in question. Circuits spread the overload more diffusely throughout the body. Both can have significant benefit. I would include both in the training prog...
Go for a long, hard uphill/downhill speed walk! Clearly define goals, limitations, accomplishments and aspirations. Martin's thoughts regarding recovery are most important. The 'wall' is an image, not a reality.
You have left open a lot of questions. I don't know exactly what you mean by change. Intensity? Frequency? Reps? Sets?
If you are referring to resistance overload training I agree that 2-3 months of adherence to a training schedule is appropriate.