To do a Feeble Grind you...
1. Approach the nearest ledge at a moderate pace.
2. Jump and land on the ledge at a angle so your front tire is on-top of the ledge while your back tire is grinding with its peg.
3. Make sure you are centered on the bike.
4. When getting ready to land the Feeble Grind shift your weight towards the opposite side of the ledge.
5. Feel awesome.
Remember a Feeble Grind is the exact opposite of a Smith Grind. So when you can finally land a feeble grind it will make the smith grind incredibly easy to learn.