General strategy tips
Attacking Villages
Place the archers so they can shoot at the enemy. Keep them close enough to still attack, but far away enough to keep them safe. Have the swordsmen walk slowly and get closer to the enemy. As the swordsmen advance, have the horsemen go to the other side of the village so they can attack from behind the enemy. The swordsmen will be a vital distraction that will help the horsemen get the upper hand.
The archers will pick off a few of the enemy as the swordsmen advance. Focus on keeping the enemy distracted by the swordsmen as the horsemen are taking position. Once the horsemen are in position on the opposing side of the village have them prepare for a big charge attack. This should be a strong enough assault to bring down the village.
Tactics
The surprise factor is the quintessential element of winning a fight. Hide your strongest troops in the woods or your Auxiliaries on the flanks.
Surrounding enemy units will make them rout! Even the strongest of their units will scatter in fear and panic when you attack them from behind with a cavalry.
Flanking your enemy should be your priority. Watch out being flanked yourself!
Using a variant of "Anvil/Hammer" strategy is useful in most occasions. To start, place a few of your strongest cavalry out of sight from your enemy, a decent distance forward and on the sides of your unit/army. Send skirmishers to provoke the enemy soldiers. Manouvre your units so the enemy soldiers attack you past the line of your cavalry. A plateau is a desirable location. Put your heavy infantry on the defensive and send your light infantry to attack full front. Send a few skirmishers to loosen their numbers. Support from your archers should stop once the hand-to-hand fighting starts. When the fight starts to get interesting, "close the circle" with your cavalry behind their backs and charge. Most units will rout, strong or weak.
Cover your sides (flanks) with your spearmen on one side. On the other should be your strongest cavalry. Behind those should be your light cavalry making regular charges and trying to break the enemy formations.
Test your enemy's resolve!
If besieged, always pretend to attack first. This will catch them unprepared. Only do so if you have enough archers/infantry, as without them it is very difficult. When you draw them near your archers' range of fire, they will scatter and try to shift position. Cease at that moment and form a compact line just in front of your guarded gates (leave your archers on those gates!). Then pester your enemy with your Aux Cavalry and slowly their numbers will decrease enough for you to confront them in full force.
Keep your general safe and close. Use him only to kill the routing units, which brings up points after the battle is over. You can use him in case a unit is badly outnumbered, just before they rout.
Attack/shift formations in groups. This way you can outmanouvre/counter your enemy's manouvering.
In campaign map, try and use ambush when possible.
Kill as many routing soldiers as possible (when they are retreating) with your strongest cavalry (if there is no general unit in your unit). This will give you a higher the chance of him being promoted to a General.