If you find conventional methods to achieve an altered state of mind are too easy to sleep while you are doing them, you can try achieving an altered state by using active rhythm, such as swimming, dancing, walking, standing, swaying, singing, drumming, or any practice that involves movement of the body. I once even propped my head up on my hands and elbows and fell into a meditative state (that turned out to be a projection experience) without sleeping because I had propped myself up.
Once you get more used to meditation, you sit or lay down and be comfortable while achieving an altered state without sleeping. A lot of people who are new think that meditation is to clear one's mind when that is actually just a method to achieve an altered state. Meditation means 'to think' and the goal practitioners have with meditation is to achieve a state of mind closer to the subconscious, which is believed to be more in tune with the energy all around us (lack of strictness and inhibitions that the conscious mind has and all that).