Affiliate Marketing Secrets

Okay, so I have the concept of advertising on twitter, which was the simple part, but how do you go about getting a decent user name?
Let’s say I was advertising for Nike, I wouldn’t just have a twitter account that said @nikerunning… That already exists… So how should I go about changing the name to something that works, selling what I’m selling, and not copying Nike?
(By the way, I’m not advertising Nike, just an example).
Anything helps!