If you've ever launched a new site, you know how hard it is to get more than a few pages indexed in a relatively short time. I was able to get a new site launched and had Google showing over 350 pages of my site in 15 days (using the "site:" operator). Want to know how I was able to get this site indexed and all of those pages cached in about two weeks? Here are the things that I consider crucial to getting indexed quickly.
1. Blog format sites. Say what you want about a blog, but using a blog (like WordPress) as a CMS can't be beat. The nature of the site, including the architecture, is perfectly designed for quick and deep indexing. Using the Google XML sitemap plugin is crucial for getting the deepest pages found by Google. I always tell Google not to index tag and category pages.
2. Pages linking to pages. You want to make sure that each of your pages link to at least a couple other pages deep in your site. This internal linking structure makes sure you don't end up with abandoned pages ("island pages") that don't have incoming links from within your site. Blogs do this natively with the "Next Post" type links. Another easy way to do this is with a "Related Posts" plugin. It will take keywords and show other posts that use a similar set of keywords.
3. A few strong links. The easiest way to grab a few high quality links from directories. My favorites are DMOZ, Ezilon Web Directory, and Yahoo! Directory (if you can afford Yahoo!). Just a few strong links is all that it takes to get Google crawling a new site.