In MTB it *seems* like it's always the responsibility of the faster rider to yield. I'm not saying this is like a hard and fast rule, but this seems to work. For example, on a descent, the descender yields to climbers - this actually is a 'hard and fast' rule.
This means, if you want to get around someone, as the faster rider you must call out your intentions and wait for compliance. Yell out and tell the slower rider where you are going. It always seems to be on the left around here, so you just call out "ON YOUR LEFT!" and the slower guy should move out of your way. If we're talking about singletrack, it's generally a simple matter to stop and lean your bike out of the way. Fire road, well, that's obvious.
If it's a fast descent, and he can't hear you, well...you just have to wait for him to become aware of your presence.
That seems to work around these parts, anyways.
Oh, and...*ahem* "...in walked a monkey with a couple of funky friends, he came right over and said this is what you'll do, you're going to get a bike, you're going to paint it blue."
Last edited by Commodus; 08-20-09 at 12:24 PM.