If I'm on stuck on the side of the road and need something that I can likely get from a passing cyclist, I will attempt to flag down said cyclist rather than simply hoping he/she asks. Reciprocally, when I pass a cyclist stopped on the side of the road I deliberately look at them and expect that if they need something, they'll indicate it to me in some way.

There are not a lot of cyclists on the roads where I typically ride and it's been pretty common for passing motorists, and even a police car in one recent instance, to slow and ask if I need assistance.