So, how i astral is really simple for me, and feel free to try it :)
First, meditate. If possible, have a candle or incense lit (if incense, i STRONGLY suggest frankincense).
Once you feel you're self getting all tingly or just really light, like you could just float away, think of somewhere to go, and if possible, picture it. You should then feel like you're being pulled there.
That's really it! Haha, hope it helped for you, and blessed be.