Por vs. Para. How can I tell when to use them?

I often get confused between "por" and "para." How do I know which to use? How can I tell? Can anyone explain this to me and give examples? They both mean "for," correct? ¡Necesito ayuda! Gracias.

Not to be rude, but I'm going to post a link to the last question of this sort (since it provides some information). http://members.rocketlanguages.com/your-community/spanish-grammar/por-vs-para This is one of the most-asked, and for my part least understood parts of the Spanish language. Yes, I studied the lesson and passed the exam, but most of the time I'm still really just guessing which one to use. Basically, there is no really simple answer (at least not that I've found).