Mostly, just go near the ride entrance and look or ask...
A couple of notable exceptions:
Star Tours FP distribution is across the way outside of Buzz
Radiator Springs Racers FP Distribution isn't even in Cars Land... it's on the main thoroughfare between the entrance to Cars and Bugs lands.
Tower of Terror FP Distribution is across the street
I think that RSR is probably the most unusual... The first time we went to grab a FP, we walked all the way down into Cars Land and were sent back up.