Basic Tactics: When faced by numerous enemies, never put yourself in a position where multiple can attack you. This means dealing with marksmen first, then dipping around your enemies only stopping to strike when there's only one adjacent. If you [A]ttack and can target multiple enemies, you're doing it wrong.
Example: out exploring the wilderness trying to find new civilizations, my companions got ganked by a kobold ambush. I was about five days' travel from the nearest town, and night was setting in. Naturally, every night saw a new pack of bogeymen after my delicious flesh. How did I survive? Tactics! I ran away until only one was adjacent, then turned and charged him. Then I stepped back and let another come at me before charging him. I didn't go for followup shots--not when other bogeymen were near. And I didn't stick around the prone bogeymen when their allies; even a dying man can be dangerous.
Sleep: Not just for the weak anymore! If you're drowsy, you're gonna fight like shit. And kobolds love to pick on drowsy marks. If you've got companions to watch your back, sleep as soon as you notice you're drowsy. This way you won't be drowsy by the time the ambush comes. And if the ambush doesn't come, it's not like you lost anything by sleeping.
Skills: Swimming is valuable, and don't let anyone tell you otherwise. While it's easy to raise all of your offensive and defensive skills, it's comparatively difficult to raise swimming and you need to be Adequate in it before you can swim in a murky pool without fear of drowning. So you might as well spend the 11 points at character generation to get there and save yourself a lot of worry.
Speculative*: Observation is also a good skill to invest some points in for those who don't like to be woken up with bolts and arrows. You can raise this by getting ambushed, but it's really a good idea to start off with Novice Observation to keep yourself alive while you train it. I've currently got Adequate Observation (having started a Novice), and I've never been attacked before I could wake up.
*As in, "purely from personal observation." I could be wrong.