Like the Rhodoks, the Nords have no cavalry. To make up for this their troops have good Athletics and sturdy armor. Additionally, from Nord Veteran onwards their infantry often have either throwing weapons (Javelins or Throwing Axes) or Longbows. The quality of their ranged weapons, as well as their efficiency with them, increases with time. The Nords also have an archer line, although they are not as skilled as their Mount&Blade/Vaegirs/Vaegir counterparts.
Initially, Nord infantry with ranged weapons behave like archers; they will move into range and shoot at enemies until the enemies move out of range or all their ammunition is expended, at which point they will charge with their swords or axes drawn.
Combat strategies
Because the Nords have no cavalry you may want to pick up some neutral mounted troops (Caravan Guards, Mercenaries, Hired Blades, or even Sword Sisters) to draw the attention of enemy cavalry.
Against infantry
When fighting on foot alongside your men, order them to stay near you. When enemies get within range of their ranged weapons they will start firing automatically. When they run out of projectiles, or when the enemy are close enough, order a charge.
Some Nords spawn with axes, which give them a huge bonus against enemies that rely on their shields to survive. All Nords generally have better armor than many comparable troops, so against even odds you may well come out on top.
If you are on a horse you can use it to draw enemies within range of your Nords' projectiles, or to distract them when they are within melee range.
Against cavalry
If you can, lead your men to the top of a hill or on the near side of a riverbank and then tell them to hold their ground there. Use the "spread out" command once or twice to ensure some space between them, which will lessen the damage dealt by lancers and horse charging. The terrain obstacles will slow the enemy horses down significantly (and possibly cause the AI to try to find another way around), but your men can freely use their ranged weapons. After the horsemen are within the ranks of your forces order them to close ranks; this will trap some or all of the horsemen, and your men will quickly kill the horses. Many cavalry troops are simply not designed for foot combat and so will go down quickly after this.
Against archers
If you have your men in a huddle they'll be easy prey for archers. Tell your men to spread out multiple times and then charge on in. If you're on a horse and have a good shield you can circle around the enemy (which should cause all or most of them to shoot at you instead of your charging men). Once your men close to melee range the archers will change their weapons and you can either dive in to help or simply sit back and watch the massacre.
Against ranged horsemen
Khergit Skirmishers and Horse Archers focus on ranged attacks; Steppe Bandits and Khergit Lancers also have ranged weapons but they use them a lesser extent.
First draw your men together and let them use their ranged weapons. When they are running out of ammunition either tell them to spread out or order a charge (as they will be a much easier target all grouped together).
Against mixed forces
Against a variety of troop types, be prepared to change your tactics frequently. If you have the superior force in numbers and/or quality (such as against Looters) you can just let your men charge and be done with it, but against equal or superior troops you will need to do at least some management to minimise your casualties.
The cavalry will always reach your men first. Use the cavalry techniques above to take them down, and then group together to take out the infantry (enemy forces generally spread out when charging which means two or three Nords may be able to swarm around individual men and quickly cut them to pieces). After this the archers will arrive and start being a nuisance, so spread out once more to lessen the damage; if your men have no ranged weapons left, simply call a charge. Only top-level archers really have decent melee equipment, so you should have an easy advantage once your men are close enough for the enemy to change to their melee weapons. If you have a horse you can ride around and mop up the ranged horsemen (if they have any) while your men deal with the archers on foot.