The basic idea of Chicken Runs is that you play as a level 1 chicken and embark on quests that require you to travel through Middle Earth and fulfill certain objectives along the way. The difficulty, as you might guess, is that a level 1 chicken has no real combat abilities, and has to rely on strategy and a few danger-avoidance skills (like playing dead, or summoning up a quick burst of emergency speed) to stay alive during the course of your adventure.
How do you play as a chicken?
There are certain quests that you can undertake at Sandson’s Farm in The Shire (located at 32.0S, 74.3W) that turn you into a chicken, and give you a time limit to get the quest completed. While you are a chicken, other non-chicken players can see you, but you cannot talk to them. (Well, you're a chicken, right? You can't really talk .. except maybe to other chickens ... :)
What do I need to do to qualify for the Chicken Run to Rivendell?
There are several quests which you should do first to qualify for the chicken run to Rivendell. All the quests are available at Sandson’s Farm, and will be done in the order listed below. Talk to Wald Sandson to get the first quest.
Which Laid First—you play as your regular character, not a chicken, for this quest
The Early Bird
The Sky is Falling
Flying the Coop – Shire
Once you have done these four quests, the quest Flying the Coop – Trollshaws should be available, and you can use that quest to start the Chicken Run to Rivendell. This quest will give you 2 ½ hours to complete the run .. actually it can be completed in less than an hour if you have an escort.
Escorts
The first four quests can be done alone if you are careful; they are fairly easy to complete if you have an escort to dispense with the various enemies and wild animals you will meet along your way. However, the run to Rivendell is very difficult to complete alone (among other things, there are stealth enemies as you near your destination). So, most people only attempt the chicken run to Rivendell with an escort. Preferably, an escort of several high-level characters J
Links
For a more complete discussion of Chicken Runs, you can look at these wiki articles; the first is an overview, and the second is very detailed:
Chicken Play
Chicken Play Guide