Por V.S. Para

Para-Your End Result or when Receiving Something! 

'--->'

Ejemplo: Para mi madre-for my mother because she's receiving it

Para las tres-For 3 o' clock, because your making whatever it is for 3 o' clock. 

Por-Your Motivation, around or near something, or when dealing with financial negotiations

'X' 

ejemplos:

when trying to say it's 'near' this or 'through' that or 'around' here...even 'down there by that' you want to use por!

also when saying: 3 for 2 you'd use por...tres por dos! 

Always use Para if unsure of which one to use because you are more than likely to be right!