Where do you find Bagon and whats the easiest way to find it ?

To find Bagon, you must look in the Meteor Falls Cave. But there is only one section of Meteor Caves Bagon lives in. I'll walk you through.
1. Start from the entrance south west of Fallarbor Town. (Route 114)
2. Once in the cave, you need to surf over to the waterfall and go up it (NOTE: your Pokemon must know surf of waterfall for this.)
3. When you are up the waterfall, go over to the part of land where there is another cave entrance. Go through it.
4. Once your through there, go down a ladder.
5. You are now in a part of the cave where strong Pokemon live, (Such as Lunatone, Solrock and Golbat) and need to walk over to a ladder going upwards.
6. When you get through that, you will find an elderly couple that will want to have a 2 on 2 battle with you and your Pokemon. Once finished battling them go up the sets of steps until you reach another trainer. He is a Dragon Tamer and he uses 2 Altarias.
7. Then you will see these wierd water ledges you can jump off. Jump down them, but keep to the left.
8. Once you are at the bottom, there is a ladder. Go down it.
9. When you get out of the ladder, there are stairs you go down. Then you have to surf. Surf up to a landing where there is another small cave entrance. Go through there.
10. When your in there, you need to surf and once you get to the end you may find an item. If not, it doesn't matter anyway, because this is the place where you find Bagon. Most of them will be around level 30 - 35.

I hope my hint has helped you!

Go to Meteor Falls. Then go up the waterfall. Youll get to a room with trainers in it an youll find some ledges. Stay on the LEFT side of the ledges. Youll go down the ladder and youll get to a room with TM02 Dragon Claw. Stay in the room for a while and you may come across some Bagons.

There is no easy way to find it but he is located at the very end of Meteorite Cave.