Ask and stop if needed. I once road happened upon a rather attractive twentysomething who she said she didn't know how to fix her bike. All she'd done was drop her chain. It seemed like such a simple thing to figure out and fix that I looked around for a hidden camera, figuring I was part of some local news piece about how many people will stop to help an attractive cyclists.

I wonder why no bike shops have started a road side repair service. You call them and they ride to your location and help fix whatever is wrong.