You can meditate at virtually any point during the day, and you can do it as many times as you want, and for however long you want (but just like anything else, don't overdo it). Some people prefer mornings, others like to do it just before bed. Some folks meditate for five minutes, others for 20 minutes, and some for an hour or more. Personally, meditating for 20 to 30 minutes works best for me. And in fact, during the course of a 2011 study conducted by the University of Massachusetts Center for Mindfulness, beginners spent an average of 27 minutes each day practicing mindfulness meditation. That's a good benchmark time to be aware of. Eventually, with much practice, and as you get more comfortable with the sitting position, you should be able to extend that to an hour or more (if you want).
Read the complete article at: http://io9.com/how-to-meditate-and-get-the-most-benefit-out-of-it-1688990555