Protect the wounded and healers by forming a protective circle around the healers and wounded when healing. This consists of the healthiest fighters encircling the healers and wounded and placing themselves equidistant from each other around the circle. 2 Fighters should be 180 degrees apart, 3 should form a triangle, 4 fours a square, etc. The strongest fighter should be facing the direction that the most danger could come from. (This is a formation named the guard formation.)
If the danger is coming from only one direction form a wall of fighters to catch anything trying to slip by. If you're standing in a spawn area, go with the circle.
The in game name for this is "forting." If someone calls "fort" or "fort up" form a protective circle at their location.
Kudzu may be used to provide a protective circle (in whole or in part) where appropriate. See The Kudzu Fortress for more. If done right, this can save the party, if done wrong, this can kill a party. So, make sure you know when and where to use kudzu.
Even in periods that seem clam, if you're out in the open and your party is at less than 50% strength, once in a defensive circle, stay focused on your zone of protection. If something spawns on the other side of the circle that the fighters can deal with quickly, do not leave your position in the circle
Taking Hits & Spreading Damage
Never allow someone to fall when you could take the hit and live. It's sometimes better to have two good fighters at 25% health than one fallen and one at 50% health. It can be a tough call, but consider the group's interests first. The most effective groups know how to take hits for each other, and how to cover each other. The goal is to avoid anyone falling, and by spreading out damage and equally as possible, means fewer people get closer to red or fall.
Reckless Member Exception
The Exception to taking a hit for another player is if the other player is being reckless and falling often because they don't know when to stay back. A reckless player is best left fallen until all the smarter members are healed so they have time to ponder the error of their ways. Feel free to remind them their recklessness means they endanger the group, and tell them to watch how the other members work together while fallen so they can learn how people should work together (assuming your group is familiar with each other), in case they don't understand why everyone else is getting up first. A reckless member is often a liability to a group.
Bricking and Dropping
If you are a brick for the group, or you can take hits and not fall. Make sure to cover other exiles that might fall in various circumstances. Exiles are usually more valuable alive, so if you can take hit to prevent another person from falling, you increase overall group survival.
Allow Dropping onto You
Bricks and stronger exiles often have to allow weaker exiles to drop creatures onto them. If an exile is having a tough time dropping something on you, more into the path of the pursuing creature to cut it off and make it focus on you. See Dropping Creatures for details on how to drop creatures onto waiting rods or bricks.