Everybody keeps going on and on about the Google Sandbox. While it does take some time to get a new site listed, I have had particually good luck with getting my last few sites listed in a couple of weeks. First, it helps to have a well-ranking site to link to your new site, this is always a plus.

When you build a new site, choose the domain name wisely, certain engines look at the domain name when assigning listings. However, it's not critical to getting into Google. Build your new site with a unique content-rich homepage. Write all the content from scratch and don't use any re-used content. Use very targeted met-tags for your homepage, 3 or 4 keywords max. Then, link to your new site from your best ranking site or get a friend to link to you. Then, start adding additional pages to your site targeting various keyword phrases relevant to your products you are going after. Try to build out 20-100 pages on your site target a different aspect of the product you are targeting. Now sit back and wait for your rankings to happen.

Now, my advice is that you launch several sites at once on different servers (shared or free hosting is fine). All your sites should be unique with unique content. They don't have to be brilliantly designed, but should be decent. Put Google Adsense and some affiliate banners on the pages and you are done!

Now go out and do that again and again!