this is copypasta from my tumblr blog that I posted some of my practice sketches about perspective. I think this is very good info to keep in mind, and is a good start for people who are new or don't get a grasp of perspective.
I will probably use this info in a future tutorial with better illustrations, but for now I'll just post it as a journal:
First and probably the MOST IMPORTANT thing to know: EYE-LEVEL!
The horizon line represents not only the actual horizon on the picture, but also the EYE-LEVEL of the "camera". Think of drawing a perspective background as if you were holding a camera. I shit you not, if you always keep this in mind, drawing perspectives will be a lot easier.