Hmm.
Only the sucky players have to "choose your fights carefully"
Seriously, the key there is "carefully". If you ever wing with Drex, you'll notice that he "carefully" picks an early war plane, flies to the thickest group of cons, trolls around a few thousand feet below most of them, and then shoots down everyone in sight. That's how he keeps his K/D over 1-1.
The last time I ever had a K/D less than 1 was my second or third day playing CK beta .8x, and I'm no more careful picking fights than any other dweeb. Sure I'm not nearly as talented in the game as Drex, Shane, or half the other addicts here, but I didn't have to play alt-monkey just to survive. I'll pick a plane I enjoy (currently ki-84), and learn how to do everything in it and then fly around at medium altitude looking for interesting fights. 1v1 isn't too terribly interesting, but I'm not going to run unless I have to. I'll even take my ki-84 to a merge and try to turn with any other plane, just to find out what kind of player they are. If they're good enough to kill me, I MIGHT run, but for the most part I'll stick around and either get them or get my butt kicked. Either way it's fun for me, and either way I'll probably learn something. That's how I keep my K/D over 1, by finding interesting fights and jumping in.
Now jumping in also needs clarification too, because it means different things. For Drex, jumping in sometimes means imitating an easy target and then killing anything that gets close. For me, it means trying to stay alive long enough to beat down my opponent enough in energy so I can saddle up for an easy shot, because my gunnery sucks really badly. So I usually don't end fights quickly even when I'm winning. That means that to have much fun, I can't be the only friendly around in a swarm of enemies. So I need to find fights that are at least somewhat evenly matched so I can take a little time to push a guy around the sky until I can get enough bullets into him, without someone shooting me first.
Another thing that really helps K/D is not fixating on your target. Anytime you're not actually pulling the trigger, you should be flipping your views around trying to keep track of all the other bandits. Sure, follow the other guy in the views enough to fly your best fight against him, but you MUST not only check 6 occasionally, but check 3, 9, high-12, straight up, even roll out if necessary to do a belly-check, or you'll get blasted right when you think you're doing ok. You must fight the highest threat no matter how offensive you are at the time, and if that means giving up an easy kill to defend yourself, then that's what you gotta do.
Another tip is to keep track of your ammo and fuel, and when you start running low on either try to work your way to the edge of the fight closest to your own field. Try not to run out of ammo when you're only 100 ft up in the middle of the furball or on the wrong side from home. It makes sense in any furball to grab altitude anytime you're not turning or shooting someone, and if you have the choice then every time you take a little breather, turn towards home and climb for a few seconds before re-engaging. That way you keep your run away home option alive when you run out of bullets or get really low on gas, and you can dive or climb towards home to get out of the fight. If you're on the deck very slow when you run out of ammo, you're usually an easy kill for anyone who happens by.
I don't know how many times I've run out of ammo and had to just keep turning with bandits. There have been times when I've gotten 3 maneuver kills after running out of fuel, because I was stupid and ran out of ammo right in the middle of the furball and couldn't run away. So I'd have to keep fighting, saddle up behind the bandit so he couldn't shoot me, and try to scare him into running into the ground by getting really close and pointing at him. Sometimes it works, but having the option to exit the fight instead is a better way to do things in general.
