Often your account, username or some kind of definable tracking id is found in your link. Most of the time we use our names, company names, childhood nicknames etc. as our username.
Recently I have been testing using different account names with some aff networks like clickbank.
The names that seem to test better include
coupon + number (eg coupon457)
discount + number
special + number
Think about this when choosing your affiliate usernames. You will see a 5-10% increase in sales vs the standard username.