Depends on what kind of meditation you are doing. Hindu/mantra repitition meditation (which is also the style of meditation of Transcendental Meditation (restricted trademark!)) tricks your brain into a weird dissociative state. If you do it for more than 45 minutes or so a day, you start getting headaches and other signs that you are doing something deeply bad to your brain. I can dig up a long article by a former teacher of TM if anyone wants it.

Vipassana meditation, which involves watching yourself breathe through your nose, is good. This is a type of Buddhist meditation and I know nothing of other Buddhist meditation except that some American Zen practitioners do meditation while breathing through both the nose and mouth.

Practicing Vipassana actually teaches you something about how your body works, and the professed religious goal behind it (other than resurrection and enlightenment and all of that) is to gain ultimate awareness of reality, which sounds very good in the scheme of big claims made by religions.

Vipassana is interesting because it requires you to intently focus on the area of your self where the conscious meets the unconscious: your breathing. Is there anything else in your body that you can successfully control or not control, entirely based on your will?

To do Vipassana, sit on something comfortable with your legs crossed. Try and sit as straight as you can and don't move at all. Throughout the meditation you should be trying not to move at all -- one of the goals is to gain control over something as ephemeral as a pain signal telling you that you need to shift positions. Careful though, if you have back problems or something and get horrific pain while sitting cross legged, try using a chair.

Half lotus is recommended for sitting unless you're comfortable in a full lotus. Close your eyes, and watch yourself breath. Do not actively breathe, but stop and do nothing and let your breath happen on its own. Just watch. You can pay particular attention to the feeling of the breath leaving and entering your nose, or the moment when your breath pauses before inhaling or exhaling. If any thought comes to mind, acknowledge it and return to observing your breath when possible.

Once you gain control over your body where conscious meets unconscious, you can pay attention to more than just your breathing. You just sit breathing while trying to be aware of every sensation your body is feeling. There's a lot more going on than you are typically aware of, such as a very slight sensation of energy coursing across your body.

It is not easy to do. Getting good at Vipassana meditation is like staring akrasia in the face and trying to conquer it. I usually end up dwelling on some recursive bad thought and get too anxious to keep going for much longer than 10 minutes. I think this is a pretty common thing for attempted practitioners of Vipassana meditation... it's tough to acknowledge that nothing really matters and that you can just sit and watch your breath for a while.

I've been in a pretty good mental state since graduating from college though; I should see if I can do better at meditation now. I haven't tried for months.

See http://news.ycombinator.com/item?id=587032 for a longer discussion.

http://www.urbandharma.org/udharma4/mpe.html is a free book with a reasonably non-mystic/technical introduction to Vipassana meditation. The closest thing to religious indoctrination is mentions that all other forms of meditation are bad, which is close enough to the truth that I don't hold it against them.

I think that mastering Vipassana meditation would reduce akrasia, if it was done explicitly for the purposes of giving yourself fewer excuses for not shutting up and getting to work. It's also just pretty cool to gain the awareness over your body (and detachment from sensations) that can be rather easily learned.

Don't do one of the retreats though, it's probably a waste of time. You don't need to meditate that much.