Finding the Right part
 

There are so many ball joint choices on rockauto and I've really no idea how to make the decision to know what parts to buy. I need to replace the front uppers and lowers on both sides of my 2002 Ranger but haven't a clue on how to determine the part. I'm not sure this is something that can be easily answered or not so I apologize in advance if thats the case.

Is this knowledge usually just acquired with experience or is there a manual of some sort that details the exact part needed? I'm kind of amazed that folks here have so much knowledge about these things. THere seems to be no end to the minutiae that one needs to know to get anything done at all. Just yeaterday I found out I needed a torx-plus instead of a torx for the bolts behind the front seats. Good lord this is going to get pricey!