Here is a list of useful tutorials related to mapping for Tremulous.
If you have no prior experience with Quake engine mapping, look here.
This tutorial briefly explains how the Vis process works and how Hint Brushes can be used to optimise it.
A solid hinting tutorial with links to other valuable hinting resources.
This is an extensive tutorial written for Quake 3 explaining the useage of Hint Brushes.
This is a Hint Brush tutorial written for the Half-Life engine. The concepts should still apply to Quake 3 and Tremulous.