Gmail labels and stars are a great way to organize your e-mail, especially if you keep all your messages, the way Google recommends. Now, you can add those labels and stars to your messages, before you send them.
When you compose a new Gmail message now, you'll notice the new Labels drop-down menu, next to the Discard button. Before you send your e-mail, select your label or star it, then when you're done composing your message, just hit Send.
When you go to your sent mail now, you'll see that your sent message has been labeled and starred.
That's it. Now you don't have to wait for your Gmail messages to be replied to before organizing them with labels and stars.