There are plenty of maps, so I won't go into detail on the locations. If you want to use the in-game map be sure to have a fully upgraded sonar equipped and constantly ping your surroundings.
More difficult than finding the plates is actually reaching a few of them. Me and my friend had the ost problems with the jumps, so just a general hint for a lot of air time, which you will need to reach about 5 of the Plates that are high up in the air or on bridges:
If you have located a high-hanging plate, dive down a few meters, angle towards the plate and boost with LT. Once you launch from the surface, you can "doublejump" with either the A-Button or LT (you will see the tail waggling). The bigger you are, the more often you can do this, up to three times as "elder".
A few noteworthy things:
-the right stick will change your trajectory and execute tricks, best stay away from that during the jump.
-don't buttonmash A/LT. a well timed approach works better
-if you get close enough to the Plate to get a target lock, you can boost yourself further by biting, closing the last gap
The whole process is a little random sometimes, be prepared to have a few moments of WTF. But once you get the boost-jump right, none of the Plates should pose too much difficulty. Just remember that the full jump potential is only unlocked from elder onwards, so some Plates will be unreachable before that.
Happy Hunting!