My biggest concern when forming a party is the puller. I'm a white mage, so the hardest to find class is already available in any party I make. Pullers make or break a party in my experience. A trained chimp can hit the appropriate function key when a character is low on hp. Pullers have to know what the party can take on, and when it's safe to pull. If a party is bad, it's almost always because the puller is overzealous, or overrates the pt's abilities. If a puller is good, the exp rolls in like crazy. As a result, I spend the majority of my party building looking for a puller with playing experience. Whilst I don't care too much if my other teammates are optimum equip, and have levelled subs, I usually make sure the person in charge of picking battles knows what s/he's doing. A levelled sub and decent equips might not make a difference in battle, but they show that the player cares about his/her job. Those types tend not to pull the IT linking goblin hoards while the mages are begging for an mp rest.