I've been trying to speed up a site I've done with Atahualpa. I've read many bits of advice about what to add to the server's .htaccess file, and it gets a little bewildering.

Any advice from you guys about the must-have bits of code you use in your Wordpress site's .htaccess file?

htaccess is a whole nother beast. Might I recommend

.htaccess made easy
a practical guide for administrators, designers & developers
by jeff starr

I just bought the book. It comes with a WordPress htaccess template.

Thanks for the recommendation, JD. I just bought the book. I got concerned because I was reading so many different suggestions from different people in different forums about which bits of code to add to .htaccess, and some people were having major issues after adding this or that piece of code. I want to really understand what I'm doing!