How do you know when to use "por" versus "para"? Especially when saying "for me/you/him, etc".

Question

anonymous · Answer

I don't know exactly how to explain it but if you write it out

Por mi
Por ti
Por el

Para mi
Para ti
Para el

Para is basically saying "For me, for you, for him." But when I use por a lot of the time it say "By me, by you, by him."

Sorry I can't offer much of a "formal" help. But I do speak fluent Spanish.

anonymous · Answer

Why is it "un regalo para ti", but "no llores por mi"?

anonymous · Answer

Because when we say "un regalo para ti," 
it means that the gift itself is for you. 
It doesn't imply that anything is BEING DONE for anyone. There's no action involved. 

But when we talk about the word "for," under the circumstance of actually DOING something for someone, 
we use "por." 

"No llores por mi" means "Don't cry for me." 

Because to cry for someone else
follows the notion that you are actually doing something, for them.