During site development, test content will have to be created so that features can be tested and styled. However, you don't want that test content to go live!
First off, avoid making any content that could potentially be damaging if it accidentally went live. The Devel module can generate content of most types for you automatically, in a way that is clearly test content and won't accidentally offend anyone.
When you are ready to go live, go through the user and content lists to remove anything that shouldn't be available. Also, browse through the entire site structure and look for menu links that shouldn't be appearing.
Sometimes, you won't have content for a section, but for layout or structure reasons it has to be in place. Make the text of the page say something like "Coming Soon" so it's apparent that the page is important, and get it resolved as soon after the live launch as possible.
