Hi regpath,
I'm assuming you're still talking about WC1, but this would apply fairly well to the other games as well.
As far as #1, it really depends on your mission. I tend to fight whenever possible, unless a mission specifically calls for not engaging (which happens in some of the Secret Mission campaigns). The key point is to accomplish the objectives. Oftentimes, though, if you want the best medals, etc., you do have to destroy a majority of the fighters.
As far as #2, yes, learn how to use the radar to turn the craft towards you. Claw Marks (the manual) details exactly how radar works, but yes, in essence you do turn to the dot to get around quickest. As far as what to do when attacked, turning with afterburning usually is quite effective for me. The following is some of my tips from what I've learned in the game (and I'm doing quite well on Secret Missions 2 at the moment).
Remember your wingman can come in handy. I generally order them immediately to Break and Attack, but sometimes you'll find targeting a specific enemy and ordering him/her to attack that enemy works better (especially, say, in an escort mission). Also realize if you're overwhelmed, sometimes wingman Break and Attack on their own and you don't have to give the order, so it can be easy to accidentally order them to form on your wing instead in a firefight, which can be a costly mistake.
If it's a patrol mission, I recommend picking off the fighters as it's easiest for you (you'll get a feel for what fighters you're best at taking down versus the ones that take more time - for example I find Dralthi and Jalthi easy because of their larger profiles and lack of maneuverability).
DON'T just keep going after the fighter you're targeting presently if you start taking fire. You'll need to circle around (I usually pull up and afterburn around in a loop) and start shooting at the Kilrathi pegging you. I don't know how many times I've died close to a fighter kill because I wouldn't break off.
If there are capital ships, and if you have time before they jump out, take out ideally all but one fighter and have your wingman take it on while you take out the cap ships. Clearing out all the fighters could mean another wing jumps in (depends on the mission). If it's a mission where the cap ship jumps out, evade and attack it first if possible, or take out one fighter, then attack it. Be careful as sometimes it's a bit easy with the way cap ships are modeled to accidentally fly into one - allow plenty of distance.
If it's an escort mission, stay near the craft you're escorting and don't follow too far after bandits. Focus on flying around your escort craft and shooting (and taunting if you can) everything that's attacking the ship you're escorting to get their attention off that craft and on you. Save missiles for these encounters where time is critical as well.
Use afterburners liberally, but watch your fuel. Realize physics is modeled, so if you boost with an afterburner and turn, get used to the sliding and drifting and use it to your advantage. Claw Marks (if you haven't read it, do) details a few maneuvers you can use with this.
Flying head-on is risky, but sometimes if you can get a few shots off (to hit) first, you'll get the other craft to break away and have an advantage/opening.
Ramming can be useful but can also mean a quick death; it depends on the situation. I tend to fly top speed most of the time, and especially with afterburners, it can be easy to accidentally plow into a slower, bigger ship, such as a Jalthi. On the other hand, against a lighter or heavily damaged ship, or if you're desperate to get a quick kill (such as an escort mission), a well timed ram to finish off a damaged enemy can work wonders.
If a wing of two or three is flying towards you, I recommend going after the craft furthest to the rear. Otherwise (for example targeting the front fighter) it's easier for one of them to sneak onto your tail. Afterburner is helpful in these situations too.
Sometimes manually flying to a point, such as in an escort mission, appears to give you a slight advantage over autopiloting there (for example, the enemy a little bit farther away from the craft they're attacking).
Finally, realize some missions in Wing Commander are just plain difficult, and meant to be that way. There's one particular mission on the all-winning path where you're supposed to defend a cap ship and it's fairly close to impossible. It is beatable (and I have), but it takes both a measure of luck and skill (as well as patience).
Good luck, and I hope some of this is helpful!
