Here are a few more tips gleaned from the questions I get from my clients.
1. SEs won’t penalize you for putting up a basic/simple (or low content) homepage and then, later, adding content. The only reasons that they penalize websites is when the site owner does obviously illegal things, like copying text from other sites, feeding the SEs one page while the public another, using text that is the same color as the background, etc.
2. Clients have asked about 404’s, and if they can count against their rankings. A few won’t, but as the number grows, so does your site’s credibility. As site cred. drops, so will inbound links, which will count against you.
3. FLASH sites: using FLASH can make your site look really cool. I can also be tough on low bandwidth users, and will cost you more to develop.
4. Website Templates: good or bad? Neither. Use them when you don’t have the skills to code your site, or you can’t afford to have someone else do it. That said, the free ones tend to limit you to very simple designs.