First of all, I don't want the Sign Up form and Login form to be on the same page, like Facebook.
I want some clean organization. To continue, I want at least one form on the index page. I don't want to do something like Stack Overflow and have no forms and only a sign up message.
On Twitter the Login Form is on the index page.
On Evernote the Sign Up Form is on the index page.
What's the best strategy?