To be honest, I did not pay a lot of attention to Freya. She has a lot of trash, and is basically a Sarth 3D fight all on her own. She has 3 Elders that you can leave up to increment Hard Mode, in exactly the same way that Obsidian Sanctum did it. We had enough trouble learning in no adds mode, so I dont recommend you start on and Elders until you really have the boss herself sorted out.
Ok, so the strats for the add packs are well established, you can go look them up for yourself. The MT on Freya doesn't actually take much damage at all, and a holy pally/ret pally keeping light up on the boss will go a long way to topping the MT up.
The main trick to this boss making sure your DPS know how to follow instructions and to stop DPS and switch targets when the RL says to. That was our main issue. So, after a little pep talk on my behalf "Pull your finger out, now hover it over the escape key. When you are told to STOP DPS hit the escape key a lot. Got it? Good."
Flayer pack - bunch up but the main trick is to know when to stop AoEing (currently we are stopping when they are at about 20%), and how fast you can take down the flayers one at a time. Ensure you have a main assist to single target them down. Healer yell out if they are going too fast. If you are taking too long, AoE to less than you are, but somewhere around 20% should be fast enough.
3 twins - all need to go down at the same time. This seems to be a bit of a WotLK favourite at the moment. We found leaving the snaplasher (the one with the debuff) till last was the way to go, and to tank rotate on that boss too. Good Vent/TS calls from RLs are essential and deadly boss mods/bigwigs boss health bars are invaluable. It's Romulo and Julienne on steroids.
The other one - this one is pretty trivial. Mushrooms FTW! Run away if you have the bomb. Aura mastery will stop the silence and help the healers until they get to their first mushroom.
Trees - we allocated about 4 ranged DPS who had to drop everything and kill the trees. Worked well.
Now, this is a CRAZY fight, there are people running everywhichway, yells over vent, splash damage, aggro dumps and all kinds of other hyjinx. But as long as you do your job, listen to the calls and make sure you are on the right target doing the right kind of damage, this boss doesn't take too long to get the hang of.