This guide should show you how to get a better rate of increase in XP while grinding as part of a party over grinding alone. However, this is only drawn from my (somewhat limited) experience and from what I have heard more experienced players say. So comments and feedback are welcome. Some preliminary points :-

Firstly, I believe the reason why grinding in a party can be faster than grinding alone is because the rate at which you kill mobs in a party is higher than the rate at which you kill mobs when you grind alone. So it is not necessarily the case that grinding in a party gives each party member a bigger amount of XP per mob. Although CoR gives a "PRTY" (i think) bonus in the XP reported for each kill in a party, when I totalled the amount given for a kill as part of a party, it was not signfiicantly different from that given while grinding alone.

Secondly, you will get party xp even though you are not part of a party. If you and a friend are close by and both do damage on a monster which then dies, CoR will give you borth "PRTY" xp. So you do not necessarily need to form a party to get party xp.

Here is how each class must grind if the entire group is to get a higher rate of XP and kills than while grinding alone :-

1) Barbarian: Must never use any powers. Only use normal hits. If you use your powers, you will zero everyone else's xp for the kill and you will never see that in your log. In fact, other players will just think CoR failed to give them xp.

2) Knight: I believe, like the Barbarian, the Knight must also only use normal hits.

3) Lock: I believe, like the Barbarian, the Lock must only use normal hits. I believe the Lock can use some basic spells (Prickling Ivy or Beetle Swarm) to hold enemies in place or help defend weak members of the party. However, a Lock, like a Conjurer, can use a spell like Dispel to improve the chances of getting XP.

4) Conjurer: This is the key guy in the party group. He will need to be the most active. Conjus need to cast every heal spell they can get, they should also cast every buff they can get as often as possible on party members. This includes Dispel. Dispel your party member even if there is no negative spell on him or her. The reason for this is because the Conju is only given XP if, at the moment of the mob's death, there were recently sufficient spells being cast on the killer of the mob. So you really need to pump out the spells to get the XP. So the spells a Conju casts could include: Heal Ally, Regen Ally, Divine INtervention, Dispel, Material Wall, Bless Weapon and so on. A Conju could use normal hits like the Lock, but this defeats the purpose of a Conju in a party, which is to heal party members.

5) Marks and Hunters: I believe, like the barbarian, the Mark and Hunter should only use normal hits. otherwise they will zero everyone else's XP gain in the party.

Ok now for a very important piece of advice: Try as much as possible, for the whole party to follow one party member and kill one mob at a time. Focus on one mob at a time if possible. This is because if you spread out and kill mobs, the XP gain will not be regular and everyone will get piecemeal and irregular XP.

The sequence in which you should select leaders to lead the choice of mob is set out above from 1) to 5). As you can see, I have set the melee and short range missile players to be a higher priority than long range archers. This is to ensure everyone has the time to get their hits in before the XP calculator is triggered.

I believe by following the above steps you will see a very fast rate of party XP gain. Make sure to pick a place with a high density of high spawn-rate mobs. I believe the above is what NGD intended when they set up the part XP system - it is just that they never explained it in writing anywhere.

As this is still very much a learning phase for me, comments and criticisms welcome!