Astral projection is really an interpretation of an experience that you have. It could apply to an out-of-body experience, or it could apply to a dream, or it could apply to a lucid dream, or it could even apply to imaginings.
So, sometimes it feels real and other times it feels vague but it's up to the person experiencing it to consider and categorize the thing that happened.
For out of body experiences, basically just relax until something other than your body begins to panic. You might feel like you're lying in the backseat of a car that's driving over a rocky road, you might feel wind that is impossible to be there, and you might hear screaming. That is all perfectly normal. Just remain calm and relaxed throughout all of it, and you'll find yourself floating around like a ghost and be able to see your body.
You can also look up lucid dreaming, for a maybe more gentle way to go astral. Of course, that way will feel vaguely like a dream, but with more experience you'll be able to know the difference.