1) Get link-backs. The number one factor in your page rank is how many credible sites link back to yours, as they are considered "votes" for your site.
2) Place your URL on anything and everything. Visit forums and be an active member (like this one) and post a link to your site in your sig. This site gets crawled frequently by search bots and they could find your site in one of these posts. Don't spam.
3) Buy ad keywords at the big search engines. Any link to your site helps.
4) Use semantic markup and CSS for layout. The thinner and more meaningful your HTML is, the more likely you'll show up in search results.
5) Use a design method called source-ordered columns so your keyword-rich main content comes before your navigation: http://www.positioniseverything.net/ordered-floats.html
6) DON'T USE FRAMES!! Your main content and navigation are not entwined this way to search bots.
7) Don't place too many folders within folders for Web pages. Keep your site one to two folders deep.
8) Many search engines don't spider dynamically-created pages that pass data in the URL, like www.somedomain.com/?articleid=14j1kj5b126. I've heard this from a couple people and this may change in the future. Set up some sort of URL sniffer on the server that can change the ?variable=value pairs into something like www.somedomain.com/articles/14j1kj5b126. Search engines will think that's a folder and spider it easier. Again, I'm not sure how up to date this particular information is.
9) Oh. Did I mention getting sites to link back to yours?
10) Be very specific about the meta keywords you use for each page. The more narrowly you define your keywords so they relate to your page topic, the higher it can appear. The shotgun approach to keywords doesn't do you much good.