Physical descriptors - Your health, what you look like, natural talents (ie dextrous, nimble, a quiet walker)
Mental descriptors - Intellectual traits, psychological makeup, mental abilities (ie punster, creative)
Spiritual descriptors - Personality, philosophy, magic (ie workaholic, nihilistic, pessimistic, in tune with nature)
Occupational descriptors - Skills and abillities that are used most often (ie police inspector, fire fighter, librarian, writer)
Defining a Descriptor
It's important to work out how powerful a descriptor is - while balance has very little to do with roleplaying, in this instance if different players have descriptors of vastly different power, one will monopolise the adventure with their descriptor and the other players will not be able to do anything. Hence you should be careful to define descriptors.
Usefullness. How frequently the descriptor is likely to be used in an adventure.
Power. How big an effect the descriptor has (ie gunslinger vs superhero).
Drawbacks. Are there inherent limitations in the descriptor? Drawbacks may also be overused in a game.
Genre. Is the descriptor appropriate for the genre of the game?
Words used to add more flavour to a descriptor. Qualifiers can be used to modify a descriptor to make it more or less powerful/useful etc..
Good, bad, elite, rookie, specialist, overly, slightly etc..
A descriptor is a minimum of one word and shouldn't be larger than a complete sentance.