To get started you should practice meditation and the other "basics", then once you have mastered that, move onto attempting to astrally project. The reason why meditation is key here is so you can easily alter your state of consciousness, and therefore project easier since altering your state of consciousness to some level is the first step in the process to AP.
Here is a method I favor:
Wear comfortable clothes. Meditate until both the mind and body are relaxed. Lie down (preferably on your back) and relax until your mind begins to play nonsensical dream-like imagery. This is called the dream-state, where you are at the point where your mind is about to fall asleep. Once you have reached this state you are ready to attempt separation of the astral body. Try to maintain the altered state and don't worry if you can't, that will just take you further from the state-it is okay if the dream-imagery stops, the point is that it is just a signifier that you are ready. Now attempt separation with visualizing your limbs leaving your body, then later on with practice you move onto your whole body. If you feel a tingly sensation it is okay and a good sign, if not that is still fine.
It takes a lot of practice but it is worth it!