This is just me thinking about things that make me give thumbs up and thumbs down when playing with new people, and thus, guild recruits.
Gets my 'aye':
Can take a leadership role in a group situation
Operates well as a member to someone else's lead
Knows how to look up the location of mobs and items without prompting
Asks before pressing "need"
Runs multiple toons in multiple professions
Enters into dungeon instances prepared - repaired, stocked on ammo, food, water, etc.
Offers buffs and other class/profession-related group bonuses without being asked
Greatful and polite (and it's my job to make it mutual, too)
Understands they are virtual strangers to guildmates and that they need to build rapport in order to gain favors
Gets my 'nay':
Guild line dramatics; whining, abraisiveness
Loot obsession (wanting into dungeons too high for them)
Regularly asking about dungeon runs but unwilling/unable to lead one
Lack of financial independance (asking to 'borrow' cash even once burns ya big)
Gets referred to thottbot, etc, more than three times in the first week
Forgets to say positive things about a guild party which helped achieve goals
Enters into dungeons unprepared and needing to rez to repair/restock after a few wipes
Pays no attention to secondary professions
Good for now. Go on about your playing :)