Find yourself and be yourself. In order to be as different as possible, you have to be you -- not a carbon copy of someone else. If you don't know who you are, that process can seem a bit scary. In order to be yourself, you have to find yourself. Do you know what it is you like? What you are like? Who are you when no one else is around?
It's important to love yourself, too. If you're not comfortable with who you are, you'll inevitably end up trying to be someone else -- or at the very least being someone who you're not to please others.