Go here:
http://www.getdare.com/bbs/forumdisplay.php?f=43 scroll down to the first post that is not a sticky post, whatever that post happens to be, the number of replies it has is the number of minutes you must spend inside a small enclosed space like a closet, cupboard, cabinet, car trunk, etc. You can't use the sticky thread because it has 0 replies. You may get lucky and get a really low number or really unlucky and get a really high number. If the number is too high to do it all at once you can do some everyday until you are done.
Try to find a space that is really tight and completely dark. You should not be able to see at all and you should have very little ability to move around.
Please use caution while doing this. Make sure you can easily breath inside the small space. You may need to take a 5 minute break every hour or so depending on how small the space is.
Be sure to let me know how this goes if you do it.