I have some questions about astral projection (AP)/lucid dreaming (LD)...

I'm a 16 yr old interested in trying it but i don't know how to actually go about doing it...it takes practice right? does anyone have any tips for me?

and also...when you AP..do you actually leave your body? if so, can anything bad like an evil spirit or something enter your body or harm it in any way? has that ever happened?

ditto for LD....nothing can hurt you right?
what are these night stalker things i keep hearing about? can you actually go in people's dreams without consequence?

sorry about all these possibly stupid questions but any help would be greatly appreciated