My friends and i have always decided on the ability scores using a random number generator app from 12-17 because we cant really find the right way to generate the numbers with dice. so my question is, how many dice and what kind of dice do we use?
The Core Rulebook offers, on page 15, five different ways to come up with ability scores.
The one I would say is most common is the first one listed. To generate one score, roll 4 six-sided die, drop the lowest, and add the other three. So, if you rolled 2, 5, 6, and 2, you'd drop one of the 2's and get a score of 13. Repeat six times, then assign those numbers to whatever stats you wish.
The D20PFSRD lists the methods of generating ability scores in Pathfinder.
There are several different dice-rolling schemes, or point-buy.