1. Shift + right click on a player, choose the team option from the interaction menu, and after the target accepts your invitation, he will become your teammate. You can also left click on a player in the chat channel and send a group invitation.
2. Hit the "O" key to bring up the Society window and choose friends that you want to team up with. Invite them to your group by clicking the Team option (A team can have 6 members at most, and teammates may share quests with each other).
3. The team is formed when the target accepts the invitation. You may move your mouse over the teammate's portrait to see his level, HP and other information.
4. To leave a team, click the X button below your portrait. Only the party leader has the right to click other teammates' X buttons and kick out them.
The party leader may also open the Society Window by hitting "O" and expel teammates. There are several other available options such as Whisper, Send Message, Add to buddy list, View Gear, Trade and Teleportation invites.