When approaching an uneven surface, such as a bump or pothole, you should rise slightly off of your seat:

Question

When riding over an uneven surface, rising off of your seat will allow your joints to absorb some of the force of impact. This will make it less likely that the impact of the surface will throw you off of the motorcycle.

Accepted Answer

So your legs can absorb the shock.

Answer

So you can jump off the motorcycle if you need to.

Answer

So other drivers can see you better.

Answer

So you can get a better view of the uneven surface.