Give the players some options for venting arguments through friendly rivalry.
If they want to fight over loot, propose that they "cast the bones" for it or proffer for them to a non-lethal duel for items. An interesting twist might be a magical item that is sentient, and will only accept to be wielded by the individual who can impress it in some (non-lethal) fashion that requires partial teamwork to succeed.
Perhaps they can work up a rivalry similar to Gimli and Legolas - who can kill the most, or some sort of other friendly, ongoing competition.
Perhaps they can attempt to fight over the favor of a princess, powerful hero or some sort of tutor/financeer. Of course, the person they're trying to impress is sending them on quests, and lavishes the most attention/reward on the individual who performs the best overall (they'll need to work together to succeed, but have the wiggle room to try and outperform the others).
Perhaps you can show them how working together helps them when they face villians who bicker among themselves; if the players cooperate while the opponents fight amongst themselves, they'll get the idea they're stronger when they're not quarreling.