While the dead soldiers will fight largely like their living counterparts, there is one key difference that you should be familiar with at all times. That is, the dead soldiers will often suddenly drift backwards with little warning, just when you're about to whack them, whereas most living opponents will stand their ground until the last minute. Try to get the deadites backed up against a wall or other obstacle whenever possible.
Melee troops will, in almost all situations, come straight at you and begin attacking relentlessly until you are dead. When being confronted by a large number of melee troops at lower levels, it is always best if you are able to take them out, or at the very least wound them, with ranged shots first. Higher-level characters can just hack away at unshielded melee enemies, and their combos will help them tear through the hordes as though they were butter, and our hero a hot knife.
Shielded enemies fight in much the same way that normal melee enemies do, except that some form of armor protects them. Typically this comes in the form of one large shield that the user holds up in front of them, however it can also come in the form of heavy bracers, a breastplate (or bellyplate), or simply two halberds that the wielder is able to hold in front of themselves. When confronted by a shielded enemy you will first need to break away the shield that the enemy is defending themselves with by using a fierce attack, before other, more swift attacks may be used. Ranged attacks will rarely work head-on against shielded enemies.
Ranged enemies operate in a much different way, as opposed to melee or shielded melee troops. Instead of rushing at you and attacking you with brute force they will hold back, sometimes in places where you are unable to reach, and pick away at you with arrows. Fortunately, when you get quite close they will often be unable to keep shooting as fast as when you are at a distance, and as a result you can dispatch them easily up-close. When you are unable to reach a ranged foe, however, you will need to use a ranged attack of your own to kill them, and fortunately it usually only takes one or two shots. Be careful though, and learn the pattern of their attacks, as ranged troops when in groups can take you down fast if you aren't able to avoid all of their shots.
Note that parrying nearly always blocks incoming ranged attacks. You can quickly advance to perfect mode against a group of ranged attackers by parrying for awhile, if you have no other enemies to worry about.
Spiders come in all sizes, from tiny little spiders, to medium-sized ones that are near the size of a Hobbit, larger spiders that are almost as big as a man, to the mother of them all, Shelob. Fortunately you will not need to ever actually fight the tiny little spiders; they are merely scattered by fire, but the others can put up quite a fight. Most spiders that you will encounter both take more hits to put down, as opposed to the humanoid enemies, and will bounce back harder. If you are able to use the Final Judgment move, then it is best to dispatch them one by one with that, unless they attack you in packs of five or more--rapid speed attacks work well in that situation.
The various champions that you will encounter, as with the trolls, are all capable of taking quite a bit more damage than regular enemies. Several of the Uruk-Hai champions are also shielded and will require numerous fierce blows before you will be able to attack them with speed attacks. Some champion enemies (and all trolls) can be taken out from afar with ranged attacks.
Fortunately, you will only need to defeat one fell beast throughout the course of your adventures, though you will also need to avoid one with the Hobbits. That said, you will never be attacked by one (unless you should prove unable to avoid the fell beast when playing through Escape from Osgiliath), but you will need to destroy one. When you do face the fell beast, simply shoot at it as quickly as you are able until it finally falls.
Mûmakil (Oliphants loaded with enemies) can prove far more dangerous than fell beasts, as they are able to plague you with a fairly continual volley of fiery arrows. Additionally, the only way to take them down would be to either plug them with a siege engine, or to fire your own ranged shots at them. Since siege engines are few and far between, when Mûmakil are faced, it is best to begin unloading ranged attacks on them, but make sure to continually dodge around or parry, as if you stay in place for too long, you will be taken down quite quickly.