There are a few things to remember that can make combat more survivable.
MAJOR TIP NUMBER ONE: SAVE OFTEN!!!! At a minimum you should save your game before accepting any quest, at the entrance to the dungeon (you can save over this slot when you get whatever it is that you're after), before a fight and after you finish resting (you can use the same slot for these). You've got six slots for saved games - USE THEM!!!
ENEMY MOVEMENT: If youre still at missile range, enemies (especially humans) prefer to use missiles or spells. You can do the same. When youre hit by an enemy, youll notice that your head bobs around. This is only your view. If your cursor is still centered, you can still shoot and hit. When you hit an enemy, they are physically moved from where they were standing. This means they will usually have to close with you again before they can start swinging. If youve knocked them around a corner, theyll have problems getting back to you for a few seconds. This can be enough time to get off a spell or two.
There is a middle ground. If you are close enough, the bad guys will try to close for melee. If you are far enough, theyll try spells and/or missiles. But there is a small space that is neither melee nor missile. Once you get into that space, you can missle them, but they wont missle you and they won't try to close with you. Experience will show you where it is. Take advantage of it whenever possible.
Enemies have problems with corners and coming up stairs. If you can catch them at a corner with a bow readied, you can make a pin cushion out of them. The same cannot be said for stairs. For some strange reason, they can shoot at you, but you cant shoot at them if you have to elevate or depress your aim. If youre on stairs, use a melee weapon. Run up, get in a couple of swings, then back off before they can get their shot in.
You can shoot through closed doors and walls. If you can see your target (however slightly) through the cracks on the side of the door, you can get a few shots off at him even if the door is closed or if theres a wall between you. If hes on the other side of a wall and youve got a pretty good idea of where (a "Detect Enemy" spell from the Spell-Maker is good for this), waste a couple of arrow to see if you can get him. Youll be surprised how powerful your bow is.
When engaged in melee with an enemy, back up a step or two. Your enemy will have to engage you again and you can get in a couple or three swings while hes maneuvering to do that.
If youre in an area where you have lots of room to back up and a serious bad guy in front of you, cast Recall and start backpedalling. The bad guy will follow you. When youre far enough from where you first engaged him, cast Recall again and (ta-da!) youre behind him. You can then run for it and lose him.
Pickpocket freely in dungeons. Sometimes, when youre pickpocketing someone whos trying to beat up on you, theyll freeze and you can get away or cast a Heal or two before laying into them again. At worst, youve wasted a few mouse clicks and picked up a couple of gold pieces.
Occasionally, when you jump or levitate down a hole, youll land on top of something thats trying to eat you. They can hit you with impunity, but you cant see them to hit back. Look down, start swinging wildly and turn around at the same time. When your weapon hits something, stop turning and hit it until its dead. Youll then drop to the ground (unless your levitate is still active) and can go about your merry way. If worse comes to worst, hit <alt>+f11 to take you back to where you were last standing on the floor (you must have the v.212 or v.213 patch installed for this to work).
If you can afford to run around without a shield, carry two weapons. Weapons have a nasty tendency to break when you least want them to, especially enchanted weapons. If youre carrying a second weapon, hit the s key and swap to your other weapon to continue the fight without having to wait to equip another weapon. There is apparently no right- or left-handedness in the game, so theres no penalty for doing this. Please note that two-handed weapons, such as the dai-katana or bow, will not allow you to equip a second weapon. However, you can do Hand-to-Hand.
On the topic of Hand-to-Hand, your hands can hit anything in the game. Some critters require special materials to hit them. This isnt the case with your hands. At the higher skill levels of Hand-to-Hand, you do as much damage as most Daedric weapons. When your Speed is really up there, the frequency of your attacks would make a Japanese chef green with envy.
If it can be avoided, dont try to take on more than one opponent at a time. If at all possible, maneuver to get both critters facing you. Then back up and let one get in the way of the other.
Critters like to pile up on each other. For example, its not unusual to run into four or five archers all occupying the same space. When you hit one, you hit them all. Unfortunately when one hits you, they all hit you (ouch!). Also, they tend to die on top of each other, which makes treasure retrieval a real pain. To avoid this, dash up and hit, back up and let them maneuver, hit, back up, hit, back up, etc. If you do it right youll have all of them laid out in a nice, neat little row.