If there's anything that will kill the inspiration/motivation to meditate, it is trying to do too much too soon, and what is too much, too soon will mean different things to different people. As a general guide, I invite my clients to begin meditating for 20 minutes each day. I get their commitment to do this every day until their next appointment, which is preferably a week away. Some clients though are better suited to 10 minutes and feel that is all they can do. In my experience, if a commitment becomes established, a client will meditate longer more often and even begin the practice of mindfulness in his/her day-to-day life.
What I have found though is that if for instance, a client is unable to return in a week's time, a fortnight tends to be too long, and very soon my client would have abandoned the idea and more than likely will cancel his/her next appointment, or even not bother turning up without cancelling. They are simply not ready to face the Zen-like challenge and may or may not seek an alternative path.
This phenomena tends to be such as shame because meditating is very a valuable process that just by practising it, a person can become more centred and expand consciousness and awareness. But commitment is needed.
Daily meditation is a discipline and can be very challenging to the ego-mind as it exposes the "inner politician" - named thus because politicians are famous for going back on promises and commitments! I am talking here about the politics of comfort seeking, and personal/spiritual development tends not to be very comfortable, because old beliefs and personality traits have to be challenged and transformed, if a person wants to experience the empowerment that Zen practice can bring.
If there is no way for any reason, that a person can arrive for a weekly appointment, I introduce another "tool" - the telephone. I get him/her to commit to phoning me on a specific day, at a specific time, a time when there is no doubt with that person that he/she will be able to make such a call. Now that home computers are in practically every other home, the use of e-mail is also used. Stating what one is committed to by phone or using the written word over the internet, has been found to be a great support. It brings into external reality the act of giving one's word, be it spoken or written.