I would highly recommend working your way through The Monroe Institutes Gateway Tapes (I would post them here but I'm not sure about the legality/rules pertaining to that, however suffice it to say they are very easy to find for free online.) Just make sure you have stereo headphones since they use what is called 'Hemi-Sync' audio.
I also use different meditation techniques beforehand to get into the zone. Here's a simple technique that I love from the very first exercise in the Quareia course:
"Turn your head to the right, take in a deep breath and then breathe out. Turn your head to the left, take a deep breath, and then breathe out. Face forward, take a deep breath and then breathe out. With your right hand (regardless of whether you are right or left handed), place your thumb and fourth (ring) finger on either side of the root of your nose where your eyes and nose meet, and place your index finger on your forehead just above the nose/eyebrow line (third eye area). Sit and breath normally, being aware of your finger on your forehead. Focus on your finger. Every time your mind wanders and you begin to think about mundane things, bring your focus back to your finger. Once your arm is tired, drop your arm and keep focusing on that spot on your forehead. See yourself breathing in white smoke and breathing out grey or black smoke. As you breathe in, imagine that the white smoke is filling your body and pushing out the stale black smoke."
Word of advice: It took me a very long time to actually be able to astral project, so I would say don't get discouraged if you can't immediately do it, it is something that must be developed through practice.
