Where to study computational geometry?

A classic work: Computational Geometry in C.

And there's also: http://www.cs.uu.nl/geobook/.

In order to solve basic geometry problems quickly, so that it runs within the time limits of the contest, you need to make certain you have a strong grasp of writing algorithms.

This page has some good suggestions on how to get better. It is set up as a two semester course of reading.

http://mrmbdctg.freehostia.com/contest_Tipsforbeginner.html