How do you use your initial consultation to pre-screen and choose your prospective clients up-front?

The initial consultation is really a two-way interview. Some posts discuss how to end arrangements with difficult clients. I'd like to hear your best ideas for setting the expectations for the client and yourself that will enhance their success and create a favorable scenario from the start. For example: A three-day food journal within the first week is mandatory. Training 2x week is our minimum schedule.