Riding a horse gives you an instant advantage against foes on foot, and adds another level of depth to the game.
 Encumbrance irrelevancy
The most important factor to remember is that the weight of your equipment has no effect on the horse's speed. This means that you can wear the thickest (and thus heaviest) armor you can afford while still fighting at your full capacity, whereas if you were to wear that armor on foot your movement speed would be impeded unless you spend some skill points on Athletics.
The horse controls are a little different to being on foot. controls the camera and your character's aim. There is a blind spot behind your left shoulder where you cannot block or attack—you can point the camera into this blind spot but your character will either aim to the left or right of it (and, if you are using a ranged weapon, the targeting reticle will disappear).control the horse's speed and turning; if you bring the horse to a stop and then push and hold again you can reverse, although very slowly. You can stop your horse instantly by pushing + to rear.
Ideally, pass your enemies on the left while swinging your weapon to the right; if you swing to the left the weapon won't reach out as far, meaning you have to get slightly closer to your targets in order to hit them.
Swords can thrust as well as swing, but this is not advisable as it is a slow attack that is hard to aim; if you are using a polearm, however, thrusting is generally your only option unless you couch it (see polearm couching).
 Weapon choices
When using ranged weapons from horseback there is an accuracy penalty, indicated by the targeting reticle growing larger as your speed increases. You can decrease this penalty by putting points in the Horse Archery skill, or by slowing down before firing (the faster you go the greater the penalty).
Wielding a two-handed weapon from horseback incurs a 35% penalty to speed and damage because you are using it with only one hand, but you are still unable to use a shield with it. This penalty also applies to the Bastard Sword and Strange Sword, which can be wielded as one- or two-handed weapons.
Unlike on foot, the length of your weapon is a somewhat bigger factor than weapon speed. While fighting with a short sword you may have to get dangerously close to your enemies, which can result in damage to you and/or your horse. If you have a choice between a short weapon with good damage and a long weapon with mediocre damage, the long weapon is probably the safest choice.
As far as reach is concerned, the best sword for horseback use is a Tempered Heavy Bastard Sword. Even with the 35% penalty to damage and speed it still has its significant length on its side. The Bastard Sword is the fastest two-hander, so if you lose your horse you can put your shield away and immediately have the full damage and speed advantages. Watered-steel Nomad Sabres and Falchions are a good pick for those who prefer speed and damage over reach, and since these are true one-handed weapons they have no penalty.
When riding your legs will be more exposed than when on foot, so you will want a shield of size 70 or higher in order to provide protection to your legs; shields larger than size 70 offer more protection but are noticeably slower. Raising your Shield skill improves shield effectiveness and can allow you to use larger shields without as much of a speed penalty. If you are using a one-handed weapon (including the Bastard Sword and Strange Sword) you should definitely carry a shield. Even if you are able to outrun melee foes, having a shield is very useful when facing enemies with ranged weapons.
 Extra slot
If you are using a combination of a polearm, melee weapon, and shield you will have a slot left over. This is the perfect place for some throwing weapons. Carrying them on horseback incurs no encumbrance penalty, and they can help you out in a tight spot.
Alternately, you may prefer to carry an extra shield in the spare slot. As well as giving you a backup if yours breaks, the second shield will protect your back against projectiles (both on foot and when riding).
 Polearm couching
On horseback, polearms provide a huge advantage. If you ride your horse as fast as possible without touching your polearm will eventually drop into a horizontal position (the weapon's speed and your horse's acceleration determine how fast this happens) and your character will "couch" it under under the shoulder. If the point hits an enemy while in this position you will deal a significant amount of damage, far greater than if you simply used to thrust at the target. When the tip hits a horseman it may damage the horse, the rider, or even both at once if the angle is just right. Bear in mind that mounted enemies equipped with spears and lances can do the same to you!
After a successful couched strike the polearm will go vertical and start to fall again; hitting or your horse slowing down will also cause this to happen. By increasing your Riding skill you can boost your horse's speed, which means there are fewer times when your horse is going too slowly for the polearm to couch.
Longer polearms generally lower more slowly and some cannot be used with a shield. The advantage to these longer polearms is that you can hit targets without having to get as close as with shorter polearms, which can help keep you out of danger. Another consideration is how effective a polearm will be when you are unhorsed; lance-style polearms move very slowly when on foot (meaning you will have a harder time fighting) but spear-style polearms can be used very effectively. Spear-style polearms can be used to block if you have no shield, but lance-style polearms cannot. Spear-style polearms can also be swung like a two-handed weapon if you aren't using a shield.
The damage a couched polearm deals can be further increased by getting a polearm with a better damage rating and by increasing your Polearms proficiency. Increasing your Riding skill makes your horse go faster, which increases the speed bonus that determines damage bonuses and penalties. Once you have raised your skills enough and are traveling at top speed you should be able to take out any target (shields included) with a single touch of your polearm tip, regardless of what the polearm's base damage is. Note that when using a couched polearm, it's easier to aim in first-person view ( key by default).
When fighting another horseman with a polearm, make sure to aim at the horse. When the horse dies, the enemy's attack is cancelled so you won't take any damage. If you aim at the rider, the one with the longer weapon will land a hit, and the other won't. If the polearms are the same length, it may end in a double-KO. That is, of course, considering both riders aim right.
 Horse choices
If you like the idea of running your enemies down with a couched lance or swung sword then what you're looking for in a horse is speed above all else. Speed has a direct effect on damage; the absolute best horse for this is a Courser (preferably Spirited or Champion), however it doesn't have much armour and may stop if it runs into enemies at lower speeds. A horse of a Heavy variety will deal more charge damage and also has more armour, but is slower than the Spirited or Champion equivalent.
If you would prefer durability over speed-based damage go for a Warhorse or Charger. These horses are extremely expensive, but they have an immense amount of armour and may be even harder to kill than you! Whereas other horses will often rear up and stop when they hit a target, Warhorses and Chargers will run straight over anything other than obstacles, horses, or friendly forces, making them perfect for dashing into dangerous throngs. If they do stop, however, their slow speed means it can take a while to escape from the situation.
If you prefer mobility over all other options, a Steppe Horse is your best option. Having the extra Maneuverability helps more than one might realize, as the mobility gained by having larger amounts of the stat easily off-sets the loss in speed one gets from switching from a Courser. A Steppe Horse is especially useful when one is being a Cavalry Archer, as the extra maneuverability enables you to keep a steady bead on your target at all times with no stopping. It also allows Couched Lancing with absolutely no dangerous aftereffects, even when charging into a group, as the horse can turn away from the enemy before it gets caught up within them. Spirited, as usual, helps.
The other horses fall somewhere between these two extremes. These particular three horse types are very expensive (especially the Charger) so if you start losing them in combat you may want to try different ones until you find one that matches your fighting style. The manoeuvrability of the horse is of less importance than its speed, as with a fast horse like the Courser you can slow down, do a U-turn, and then head off again, only being in danger for a very short period.
The Heavy Hunter is by far the best all around horse in the game. It combines speed, moderate maneuverability, and a solid punch when charging. The major "drawback" of this mount is when facing Khergit Lancers as this mount is a bit slower than their courser,but a proper strategy will more than offset the speed disadvantage. When properly used, the Heavy Hunter can help you decimate enemy heavy infantry and cavalry alike.
 Horse vulnerability
Just like people, horses take extra damage when hit on the head.
Spirited, Champion and Stubborn horses may become "normal" horses if hurt/killed too much. This can happen while in battle (in such case you will be warned with a message stating that "Your horse has become lame" or after a battle. In the same manner, normal horses may become lame and lame horses may die for good (this means they will dissapear from your character/inventory). Note that lame horses, whether they became lame because of an injury in battle or were bought as is, will heal over time when put in your inventory to become "normal" again, and horses in your inventory makes you travel faster on the world map (Horse type/condition doesn't matter for this, they all give the same speed bonus). Normal horses can't heal further and can never become or re-become Spirited, Champion or Stubborn.
Polearms are great for countering cavalry. When on foot, landing a thrust attack will make a horse rear (and thus stop it) under certain circumstances:
- The horse must be running. This won't work against walking/not moving horses.
- The horse must be hit on its front. Attacks from the sides or rear may not work (not tested).
- Works with any Polearm, used with one or two hands, even staves or couched lance-type Polearms. Doesn't work with any other weapon.
- Works against any type of horse.