1). There are many ways and it isn't the same for everyone. You must chose the way you feel like. I often say a mantra for calming/AP but a friend of mine can't even relax enough to get a little sleepy when doing this. He is using imagination. There are many ways on this site...and others.
2). Some say that you must return to your body but I believe you return on your own. This is my personal belief...but grounding after a succesful AP or even a simple meditation is indicated from various reasons.
3).Of course we can.
4).Your choice. This appears as how you want to be. Matter in astral world is energy and you can manipulate it with the mind.
5).You can't bring something from Astral to the this world but you can influence so you may have that object in the future.
5).You can't kill yourself. If you die in a dream, are you dead? It's the same thing.
This is what I believe, so if I may be wrong, sorry.