You can't spell "selfie" without "sel" (minus an L), so think of it this way: You're selling your look. By the simple capitalist laws of supply and demand (hello, Econ 101!!!) you need to leave the people wanting more, according to my sister.
Basically, don't just go around throwing up random selfies like the world is ending tomorrow. It's not a cute look. Here's what my sister had to say about selfies:
1. Be "spontaneous and fun."
2. "Not all the time" aka DO THEM SPARINGLY. "If you think you look good in a selfie fine Instagram it but wait a while before you do it again."
3. Selfies are "not to be taken seriously."
4. "Selfies should only be when you have a GOOD one."