Step two: Making your website accessible.
For the most part, accessibility has to do with adding tools to your website so that anyone can use, navigate and see your website.
Dive in
Mark Pilgrim's Dive Into Accessibility is the ultimate guide to accessibility. Although it seem daunting ("30 days?") a lot of the tips suggested there can be implemented in an hour. Allow me to highlight a few key things from his excellent resource:
Day 15: Defining keyboard shortcuts (read it here)
This is one of the most overlooked, yet most amazing tools that every browser has. Try it: press Alt and 1 (or control if you're using a Mac) and you should jump all the way to the bottom of this page, where you'll the link to the next page. By defining accesskeys you help those who have difficulty using their mouse, or just simply want to get around more easily.
Day 26: Using relative font sizes (read it here)
Ever visit a page and squint because the font was this small? Did you ever try using your browser's text size capability, only to find that the font remained that small? There are plenty of people who don't have as good an eyesight as you do, and taking a moment to consider them is particularly important. Use relative font sizes, that is, 100% rather than 12px, 120% if you want something bigger, etc. That way your browser can readjust the font size via the browser.
How to degrade gracefully You want your website, when it's stripped of the fancy images, background colors, Java Scripts, music, and all the added stuff, to still be legible, easy to navigate, and perhaps even aesthetically pleasing. It's essentially putting in "Plan B"s into your site so that even if some features aren't supported on someone else's browser, everything works just fine. Dan Tobias does a good overview of graceful degradation on his website, so I suggest you look over it sometime. To see how this page looks stripped down, click here.
I hope it hasn't been too horrible up to now. You needn't to integrate everything that Mark says. Making steps towards it is an effort worthwhile your time.