I try and think of names that follow along how I want my character to look/feel. Example: borderlands, Lilith (named Serpentine) is dressed in shades of green. Fallout3, Charlie the Character, all-around character. Whereas another Fallout3 character is Peppermint who has Bright red hair.
For non-customizable characters, I just use my Gamertag R3bellation (if thats the default save) or my real name, Matt.