Post your tips for fighting Chaos armies here.
Chaos has no shooty units. So march block them, and shake them to the ground, and hit them with BTs.
Be very careful with the knights. Keep your bts on hill. Earthshaker his but.
If you playing against Khorne:
1 The Khorne Player has no magic but have many dispel dices so magic isn't the best versus them.
2 The Khorne Player usualy takes many Knight units so you have to take many BT's and a Earthsheker. Blunderbusses in this case are useless.
3 The Khorne Player has frenzy special rule on his units so take many hobbo or hobbo riders units as cannon fodder and try to sneak with them in flanks so the frenzy rule worked on our side.
Much as I dislike doing this as a chaos player... watch out for Tzeentch armies as they are immense in the magic phase, especially since all those extra dice go into the communal pool. Your hobgoblins will be especially vulnerable to indigo fire of change, which can lead to a unit of horrors apppearing in the midst of your army. Big units of screamers and furies are also to be feared. The lore of shadows is also nasty. A bray shamen with this law and the staff of darkoth is one of the nastiest tools at a chaos player's disposal, especially if the beast herds lie in ambush. In the end, a static defense is the best possible tactic against chaos, but make sure you guard your war machines extra carefully
Chaos armies are easy enough to beat. It's simply a matter of finding which troops are most likely to rip you open in combat and then shoot them to bits. Blunderbusses are more useful against the Marauders and Chaos Warriors and you should have the S5 bonus most of the time as the foe's shooting will be minimal. If there was one unit to look out for it's the Furies. Straight up. These things have caused me more woe than Chosen Knights purely down to their speed. Blast them with fireballs as much as possible. And don't forget that that a quake roll will also cut their flying movement in half too.
Chaos' shooting may be bad but their magic will get you if you don't watch out. It's not stoped by 'shakers, and since Tzeentch characters and daemons can cast and fight, they don't have the trade off between magic and combat that most armies do.
A Chaos army will probably have no shooting and little magic.
This is a great army to use a Taurus against - march block, hunt wizards, hunt fast cav, burn things from behind. A Taurus is a good choice versus Chaos.
Use your Bolt Throwers against his Chaos Warriors or spawn. Use your Earthshaker to slow down his Knights.
Put the Centaurs on the Flank along with HogGob wolf riders and Taurus and try to get in behind him.
Take a Great weapon or a strength boosting magic item for your heroes - it will come on handy for killing spawn and high armour save Knights or warriors, or even autokilling Chariots if you tool your Lord correctly.
Blunderbusses are fantastic for killing Beast Herds. Position them near his Beast herds (or if he out-deploys you then stick them near to forests or other terrain his Beast herds might try to make use of).
Hobgoblins of course for diverting charges as per usual, always a good tactic against Chaos. If he has a cheesed out unit of Chosen Chaos warriors sacrifice Hobgobs to keep them away from your CD warriors.
Well here are my Tips for fighting Khorne (I have a Khorne Army myself):
1. Shoot the Knights. Never let Chosen Khorne Knights hit your battle line. They hurt. The best way to deal with these is to shoot them as much as you can.
2. Having lots of expendable units is useful as you can. These are usful to lead astray the nasty frenzied warriors you may face, taking them out for a turn or two (allowing you to shoot them more).
3. Watch out for flesh hounds. These are quite fast and can shred your warmachine crews to peices.
4. Leave the Sorceror in his tower. Magic wont do you any good againt the large number of dispell dice your oppenent will have.
5. Your oppenent will have no shooting and will therefor be marching towards you as fast as he can. Use a solid line of blunderbussers to shoot him down as he marches towards you.
Edit:
6. Another great trick is taking a large unit and a sorceror with lore of death. Make a unit cause fear and your can often autobreak them. This is good because chaos armies dont always have the largest units.
Try and tie-up spawn with your even cheaper hobgoblins, it's unlikely that they'll run away with their outnumbering and rank bonus.
Concentrate fire on their toughest units (knights mainly). Chaos Warriors are rarely taken these days due to their soaring points cost so I'd try to keep the template weapons to a minimum.
Bolt throwers are your friends - actually pretty much any weapon that ignores armour can be your friend.
Blunderbusses are very useful, as you should get at least 3 opportunities to shoot at a unit
1. When it stops about 12" away;
2. After they've moved into charge range; and
3. The Stand and Shoot.
Granted, it's not perfect but high strength shooting is hard to deal with for chaos.
Now magic - granted Khorne armies have bucket loads of dispel dice, but the others don't, and if you don't have a sorcerer of their own, they can get raped in the magic phase, and that is never a pleasant thing. Your best choices for lores are either metal or death. Metal is invaluable with the high armour saves that Burning Iron and Spirit of the Forge are made for. While death can do nasty things to Chaos' high Ld.
If a Daemon Prince/Greater Daemon feels cocky and charges a unit all by himself, this is a good chance to make use of their Instability rule. Take a Hero with the Black Gem of Gnar. A butt naked Hobgoblin Hero would fit the bill nicely, aslong as he is in a unit to get that all important combat res. Get him to challenge said Daemon, lock him in place with the Gem and bang! No more Daemon.
use all range units, except for 25% of you army with be hobglins at 2 points each. so for 2000pt you will have 250 hobgoblins. this will buy you time before they get to you "shoty" units and hopfuly they will have very little stong units left then punch hard with bullcentars that will then flank some units of chaos.
Ta-Da you win
Except don't buy bows for said hobgoblins as it is a waste of points. You'll be unlikely to get many hits, those that do are going to have a hell of time getting through Toughness and armor saves.