Clicking when I start car.

How can I tell the difference between my starter or my battery going out?

take them both to autozone and get them tested.

if its a newer battery you may want them to check your alternator (while it is still on the car)

It would be reasonable to expect the starter to just click if the battery voltage is low. What you are probably hearing is the starter solenoid. Charge the battery up, or get a jump and see if the starter turns over. Of coarse, make sure the battery cables are clean and tight first. If the starter works with the correct voltage, then have the battery tested after a full charge. If the battery tests good then have the charging system tested. Most parts supply houses will do these tests for free.