Originally Posted by
Auror.
Go by whatever your unabbreviated/unnicknamed name is for a while i.e. full name, and see what nicknames people come up with that you like and sound like they fit you.
If you find someone starts calling you one of these and it makes you cringe, or just is weird to respond to, it's going to be harder to change it once you've decided on something. Whereas you come across a nickname and find it fits, it's easier to shorten or swamp from your full name.
You might actually find you like your full name better than you think, or someone might come up with something you would not have thought of yourself.