There's a thread called P-type vs L-type in this section if you look through it that should give you alot of info on things to look for.
The easiest way to tell is to look at the flares, in most all cases this will tell you which you have. If the flares look like they are a seperate peice and stick out in the front and back then it's a P-type, if they bulge a little in the front and a tiny bit in the back that are part of the rest of the panel it's an L-type.
Maybe we can have a mod here make a sticky thread with some of the more frequently asked questions and a READ ME FIRST type stick thread that lists some general things as well as suggesting to do a search first.