This was just recently posted on the live boards, but overall I think this is a good resource – especially for those new to the game or MMOs in general.  He does a good job of explaining not only the mechanics but also the terminology which for many cause all sorts of confusion.

Even for seasoned players there’s some good info in there as a reminder of some of the things we should be doing but sometimes forget or are just too lazy.  I find a lot of these points are really critical when doing the 3-mans and I’m sure with skirmishes they will become even more important as there’s more potential to group and more things going on.

Rain’s Guide to Grouping

LOTRO Forums Discussion

I did post on the LOTRO boards correcting his LS+IHW statement and pointed him to some of my other posts to fill in the warden section.