It should have a clear objective that will lead to a specific action or outcome. Work around the answer as specifically as possible. Don't be vague. You get the picture. The mind hates confusion.
Visitors can only do one thing at a time.
If they have to do too many things on the front page, they will do nothing. If you want to offer a variety of different options, then try to focus on one alone and create other pages that are each respective to a particular action, and then link them together at the appropriate locations for flow. In essence, keep your message focused. Use one major theme and revolve your message around it. Newspapers capitalize on that intrinsic human behavior, which is why front-page headlines, pictures, and news articles are always carefully selected.