Ok let me help ya...
1. Go to Meteor Falls.
2. Use Waterfall.
3. Go all the way straight, until you're near that Dragon Tamer. (Which you probably beaten alreay)
4. Go down, but lean to your left side, so that you could go the other way instead of go to the same place you were before.
5. Go into the entrance. (There should be some stairs there somewhere)
6. Surf your way to the right corner.
7. Go into that little entrance there.
8. Surf up again until you'll see a pokeball that should be a TM, I think.
9. Run around in that little rectangle, and eventually a Bagon should appear.
-Ps. Sorry if you don't understand. It's complicated to show you it without a map. --'