What Best Practices should be undertaken for a Website that needs to "scale out" to handle capacity? This is especially relevant now that people are considering the cloud, but may be missing out on the fundamentals.

I'm interested in hearing about anything you consider a best practice from development-level tasks, to infrastructure, to management.

Use your best judgement when posting multiple answers, since it may make sense to post them separately for voting purposes. (hint: you'll likely get more reputation points for many small answers than one large answer)