my article I copied off of

There are three ways to use the beasts, either as a pure beast force, backup for a mortal/demon army or mainly beast with mortal/demon allies. I've only use them as a pure force, so what I say about the other two options is based on my observations of other peoples armies, not my actual game experiances.

Using a Pure beasts army with mortal/demon backup

So when you start your army, you probably want to start with heroes. Your general will either be a Wargor(in less than 2k), Doombull, Shaggoth Champion or a Beastlord. Even with the worse profile, I like the beastlord more than the Doombull or Shaggoth because of ambush, the coolest part of beastmen. With the doombull or shaggoth your army will just be a frontal assault army, something a mortal army is much better at. Use mages if you want, they're sort of hit or miss, but if you take one, take the staff of darkoth.

As I said before, the ambush rule is the best part about beastmen. The ability to have gors appear behind dwarves or other defensive armies is amazing, and will make your opponents s*** themselves. If you plan on ambushing, take the horn of the great hunt.

After choosing your heroes its best to check out your core units. Beastherds are the best choice, as the can ambush, skirmish and get rank bonuses. Taking them also allows bestigors, which are always helpful.
Bestigors-great unit, with t4 and heavy armor they should be able to take some arrow fire before getting into combat. Try to get the charge with them, as they should be able to break a unit in 1 turn(excluding undead). Some things to note about them, they cannot ambush, and only one unit can have a mark. dont ask why, but its in the book. Chariots are good on the charge, but after that they are sort of pathetic. Warhounds are only usefull for screens and increasing your ambush count.

For special choices, you have centigors, your semifast cav unit, which can win you a game or ruin your battle plan, depending on your drunken roll. Minatours, Ogres and Dragon Ogres(A rare choice) are expensive, cause fear, are fast and have a lot of attacks, and its probably best to get them great weapons. Dragon Ogres are the best, but are massivly expensive and have the worst models. I like ogres more than mintaurs as they are 5 pts cheaper and have a better armor save even though they have a lower Ld. and cant get marks. I dont like trolls, because stupidity and low Ld. are never a good mix. They are good against knight though, so if your facing brets they might be a good choice.

For rare choices, you have the Dragon Ogres(touched on above), Spawn, giants and the almighty shaggoth. Spawn are slow and even though they are ok in combat, I dont like them. Giants are fun and good in combat sometimes, but great weapon units tear him apart and its hard to avoid them when you constantly roll 'pick up and...' The shaggoth is immense and deadly, especially when marked. Use it in big games, but it will attract every RBT and cannon your enemy has.

If you want to add mortals or demons to your list, I have a couple suggestions. Use furies or screamers for taking out warmachines and causing havoc, and use knights if you want some badass cavalry, but I dont really think mortals or demons are a great addition to a beast force.

Ok, its been a while but heres some tactics-

Your main advantage is ambush. I cant say it enough. It'll turn the entire tide of the battle if its used properly. If youre going to ambush, give your general the horn of the great hunt if you want it to work at all. Foerenders in your beastherds is close to necesarry, as his better stats (mainly Ld. and S.) makes your beastherds deadly in combat.
Another one of your advantages is the raiders formation. with M.5 and skirmish, you can run circles around your opponents and hit them almost whenever you want.
Use your monsters to hit your enemy's lines along with your bestigors and chariots to hold the units in place and circle your beastherds around them and hit them in the flanks (rear if you ambush.) Remember, you cant beat chaos warriors in combat with a single unit unless yourereally lucky or if its a shaggoth.

If you want to add beasts to a mortal or demonic horde, these are my ideas but as I said above,I dont have any experiance playing them, its just what I've seen other people use.

Beastherds are good to hold flanks against fast cav, skirmishers and flyers and is good as a flanking unit. The doombull or shaggoth champion would be a good lord choice in a 3+k game to add a little more punch to your assaults. Maruader fast cav is normally better than centigors, despite the worse models. You could use bestigors as a cheaper, faster unit of warriors with great weapons, as they have a decent ws and their I doesn't matter but its all up to you.

In conclusion, if you want an armored, frontal assault army go with brets or a mortal chaos herd. If you want a quick, skirmishing combat army, Beasts might be for you.