Finding TM53 in Pokemon Black and White, the hot-ticket item that teaches Energy Ball, is not that difficult. Getting to the spot where it's sitting, however? That is. In order to get Energy Ball, you'll need to do the following:
- Beat the Elite Four once
- Beat Team Plasma's N and Ghetsis
- In short, beat the game
Once you've done that and regained control of your game, head to Nimbasa City or Opelucid City, your choice. Both have eastern gates that will lead you into new areas of Unova that you couldn't previously explore, but which are now fully accessible.
Proceed along either route - Opelucid City is much closer, as it's practically right beside where you need to go - until you reach Route 12. You're now in a small sloping area just west of Lacunosa Town. There are various trainers on this easy-to-navigate route...
... and, roughly in the middle of the area, you'll find two trainers flanking an item ball. This is TM53, the desired Energy Ball. Snag the sucker and be on your way.