Lesson 2: Tactics
You have a series of activations, as does your opponent. If you can force his hand and dictate what order each activation is resolved, you limit his tactical flexibility. In order to get those very important charges in, you must learn some of the disruptive tactics that allow you avoid the charges you really don't want to receive. There are a few tried-and-true maneuvers here that will allow you to dictate how the opponent uses his activations. You'll often see the words Alpha Charge mentioned here and there in the warmahordes community blogs and forums.The Alpha Charge happens when a player has luck or skill to pull off charges with everything that he could want to charge with, in a single turn. It usually means that the charging player gets a huge lead in that game, and can be completely crippling. The receiving player simply does not have enough models left to dent his opponent, and regain a foothold in that game. You should do everything in your power to avoid the alpha charge, and quite a lot of the tactical maneuvering in the game has to do with ways to set up or avoid charges. The Alpha Charge is sort of the natural default situation that will happen if you don't play with a level of tactical awareness. You rarely have to take a charge unless you want to, because you can simply measure how far away the opponent can reach after moving (the so-called Threat Range), but then again, you cant stop and stare down each other either. Someone is going to be charged, as there are control points and flags and great fun in the middle of the table. Just know your options:
The warmahordes tactics 101 is about piece trading. Like chess, you do not want to sacrifice your own queen to take a bishop or rook unless you are forced to do so. If you lose your own queen, you want to take the opponents queen with you. You might say that if a player wants a model dead, that model dies, even 'casters and 'locks. Very few models will survive a charge from the right model of the opponents army. This golden rule is only changed by adding (sometimes many) layers of defenses: buffs, intervening models, spells, positioning in terrain and so forth. Thing is, if you commit a model to charge into the fray to kill something, you can be pretty sure that the same model is destroyed the next round by something else, if the opponent wants it gone. If X charges Y, then Z charges X. You could say that the game is about presenting models for the grinder in the right order, in order to have the right 3 models left in the end, but that's not quite fair. Sometimes you can stop a piece trade from happening by applying pressure in other places. Force a player to choose which loss he wants to avenge. While this way of thinking might have merit, it does not simply translate to always going for the most expensive models, points wise. Piece trading is always situational.
Get in the way, put up speed bumps. You can screen in different ways with different units, but generally its about taking a cheap unit and putting it in front of the rest of your forces. Is often very useful if you need to get within distance, but you have to get within charge / shoot range of the enemy. A screen of units can be a literal wall of infantry, or they might be a more dispersed group in front of your forces. While the first might benefit from certain bonuses from being near other models, the latter complicates the opponents next move a lot more. If you face multiple enemies, or enemies with several attacks, option 1 i rarely advisable. If you put a group of models forward, the enemy has to remove those to clear his charge lanes, and he must use precious activations doing it, or ignore them and receive the free strikes. Models with reach and good speed are excellent screeners. If you go deluxe, vengeance is a nifty trick, as is a corpse / soul token gatherer well behind them, because you know some (all) of them will die. You dont have to screen with the entire unit. Often a small amount of guys can make a big difference, but that depends on enemy and game size. When you screen you want to cover as much board as possible, and if the opponent wants to clear them out, it should require as many models (or even activations) as possible.
The jam is essentially the same logic as the screen, though it works a little different, by shoving a great many models into the opponents formation. It is used if you cant connect the charge as you fall short by a few inches, (or somewhat rarer, if you want to get into the relative safety vs shooting with a DEF bonus for being in melee). The jam is often useful against a ranged army. Just run into contact if you have to; being in a losing melee game is a better problem than being stuck in a one-sided ranged game. Often it is the same deal if you run into an efficient close combat unit. The jamming unit you run into combat is going to get brutally slashed, but losing cheap infantry troopers is often a better problem than allowing their charge to connect where your opponent wants it to connect. Whichever the situation, the jam works the same way. You run way up their faces, and you position a unit so each of your guys threaten as many models as possible, preferably as many units as possible. The further in you can get them, the better. If you can threaten hiding support solos, that's one more of the opponent's activations that is disrupted. Force the opponent to clear these forces away using as many of his activations as possible, before he can think of moving the rest of his forces forward. If you get the opportunity to jam gunlines, the better, because they can't reliably remove the threat themselves if they are in melee - forcing the opponent to use another activation to clear it away.
The reverse of the above is the unjam, or counter-jam, or anti-tarpit, and should preferably work well against both jams and screens. You want to cheap options for this task, since committing expensive models to clear cheap models is really inefficient. Chaff removal models are models with rules that allow them to remove large quantities of infantry that gets in the way. The screen is countered by huge spell blasts (some warlocks and warcasters are the best chaff removal models in the game), or trampling heavies, or you can ignore the screen using models with parry, and defeat it using berserkers with reach. Of course, screen removers should preferably be low on numbers, so you dont remove their screen just to replace it with your own screen and end up in the way of your own ready-to-charge monsters. Jamming models are more tricky, because there are a few tactical options that are taken away when they are up your face. Reach and several attacks works, as does Thresher, if at all you can avoid hitting your own guys. Otherwise Side Stepping infantry with more attacks, or models with Overtake are excellent at murdering jammers, because they can remove a model, move and remove another one. Whichever unjammers or screen removers (units, solos or whatever) you want, keep them in the second line, so you can move them in where the jam annoys you the most. The less space they take, and the faster they are the easier it is to use them without having them get in the way afterwards.
High Threat Infantry
Infantry with Weapon Masters, you really want to attack valuable targets with. If you have your valuable high threat infantry bogged down with a cheap jammer unit, they can't resume their brutal armor-cutting until you've unjammed them again (or they unjammed themselves).
Line of Sight Management
Putting up clouds on the table, creating terrain or cover, or preferably obstructing line of sight completely is a wonderful way of dictating where the opponent's offensive output is concentrated. Making it difficult to see/hit squishy models by creating vision obstruction is a neat trick. If you can't hide everything at once, then tempting your opponents low-damage models to attack your neatly presented armored models by hiding all squishy guys behind clouds also works. If you can't be seen, you can't be targeted. So while models might run or move normally, but if you can't see a target, you can't declare a charge or shoot. Eyeless sight and spray attacks counter some of these benefits, but other models might be in trouble. Many models can create terrain or vision obstruction that will dictate the next choices of the opponent.
The Brick Deployment
You'll often see models bricking up in the middle of the deployment zone, as far ahead as possible. Most scenarios are fought in the middle of the table. Short weapon ranges or bad SPD stats require models to minimize their travelling distance to have an impact on the game, in the middle of the table. Space becomes very scarce in the middle of the table, a ressource in itself for slow models. You might want to position these as close to the center of the table as you can, preferably without splitting up your forces too much due to terrain. Sometimes this is not feasible, but the reason for this is often if scenario zones and flags are widely scattered. Tight deployment also allows a certain flexibility as you advance, since you can adjust each model to the left or right depending on enemy movement. Of course bricking poses a challenge if your opponent can capitalize on it with AOE's, and it has happened before that they simply get in each others way. "Unpacking" your brick in the following turns is often (not always) a good idea.