There's a method which I've followed and had great results with. Make sure you try it on a day when you don't have work/school/anything else the next morning so you can sleep as much as you want:
Go to bed between 11 pm and 1 am. Make sure you set your alarm clock to exactly 6 hours later. When you wake up, stay awake for an hour and read/watch material related to Astral Projection or just think about it. Then after exactly one hour, go to bed again. But before you go to bed, make sure you affirm that you are having an astral projection after you sleep. Keep affirming and thinking about astral projection until you fall asleep. Be patient, as it is usually hard to sleep, but eventually you'll fall asleep.
Now 2 things will happen for sure after you fall asleep:
1)You'll project astrally
but if this doesn't happen:
2)You'll have a lucid or an unusually vivid and realistic dream
I've tried this for many times and not once was a time where nothing happened. I've always had either an astral projection or a lucid dream using this method.
This method also works for lucid dreams, if you change the affirmation accordingly and you read/watch lucid dreaming-related materials during the 1 hour you stay awake.