All good answers. Lack of commitment to an expressed interest in training is at or near the top of the list. I would ask if not now, then when? I encourage a potential client to realize that if he/she is just starting a training program, there will always be reasons to wait. I agree with the suggestions to offer a free session so the prospect can evaluate your style, as well as to, hopefully, recognize that his/her training may not be as grueling as he/she imagined.