Hi achilles and welcome to the Cruiser's forum. You might flesh out some more details like where you are and where you are willing to go to hook up with a
boat.
If you are near
water already there may be opportunity at local sailing clubs. Particularly if they have
race days.
Racing skippers are often looking for crew.
Google for yacht clubs and sailng clubs in your area. Also if you can swing the
money it might help to take a
dinghy sailng course or a keelboat course to give you the basics.
Good luck!