Questions about Ledge Fishing?

I'm relatively new to ledge fishing and have some questions. I typically fish a shallow river system where the ledges are 10' deep or less and the main channel is around 20' deep. The water is typically pretty dirty with visibility at 12-18" max.

1) It seems like these ledges are too shallow for me to idle over and immediately fish the best looking spots. Is this true? Where is the break point on spooking fish. How long does it take for the fish to settle down after idling over?

2) In this situation how much water needs to be behind the ledge (how close to the bank)?

3) Where are the best ledges typically? Outside bends, inside bends? Close to spawning areas? Close to major feeder creeks?

4) What's the best way to find the sweet spots on long ledges?