One thousand ugly free-user watermarks - Game Maker thread

So, guys, can anyone instruct me about what resolutions work best for gm? I've read some things about the screen not stretching properly or the game running too slow. Also spirte sizes, can i go crazy and make objects the size of the screen? Should i use only even numbers so they re-scale properly?

I also updated the first post with some helpful links provided by you guys and i'll keep adding to it as you post them, maybe i'll post a list of projects done/being done later.