Nicknames usually come naturally, but if you want to make one for yourself, you'll have to do some thinking. Most of the time, friends are the ones who come up with your nickname.
However, to make up a nickname for yourself, there are steps you can take. First, try using a nickname generator, such as the one on selectsmart.com. The hard part is branding yourself with that nickname afterward. Ask your friends to use the name, put the name on your sports or club T-shirt, and correct people when they use the wrong name. Some people end up using their nicknames all the time, and some even legally change their names to their nicknames.
The best way to get a nickname is to be known for something. Your friends might decide to call you by your last name or call you a shortened version of your first name. Many people use a shortened version of their first names as nicknames; for example, Katherine might go by Kate. This is the easiest way to have a nickname because your friends already know your given name. And finally, if you have a nickname you don't like, you don't have to use it.