I'm not much for the whole score thing BaldEagl, but here's what works for me-
One- I never take less than 100% fuel in the hogs, and that includes the -4. With the -1D, -4, and -1C I always also take 1 DT.
Taking off from rear base doesn't matter, neither does climbing to a fairly safe altitude. My normal routine is to take off from one base back, and climb to 12-14K. The climb and RTB time will count against your K/T, so minimize the RTB frequency by taking enough fuel. I always run out of fuel before ammo. I ditch the DT when I get serious about killing someone.
Hunt the furballs, but hunt the edges. Make sure you're not wasting your time where there aren't enough targets, or where you need to share targets with others. I'll lift if the dar appears "equal" between my country and my opponents, but won't if my country looks dominant. I need at least a 50% full dar. Try to seperate out just one or two bad guys at a time. Fly smart, but also be aggressive. Being too timid won't help K/T. Neither will flying back to the fight because you got careless and died.
IMO, the number one factor that will help your score/stats/success rate or whatever is hit%. That's because hitting what you're shooting at kills what your shooting at. Quickly. With minimal ammo. That's huge... If I was going to concentrate on any one aspect of my "score", it's hit percentage. And I'm not talking about "cheating" yourself by falsely elevating it by being selective with your targets. Don't kid yourself, be honest, and appraise your faults. Don't worry about what someone else thinks when they look at your score.
Hit percentage does this- finishes the fight quickly, with minimal E-loss, SA loss, and ammo loss. This means you don't need to RTB for ammo as soon, you don't have to dive out and escape (since your fight is quick, you have much less chance of being disturbed). Finishing the fight quickly helps K/T, as does minimizing RTB's. Less time spent in any one fight also means you're looking for your next target sooner. High hit% equals more kills- instead of missing and possibly getting killed by your opponent, or dragging the fight out too long and having unwelcome guests arrive... This will also drag your K/D and K/S up. The F4U's carry enough ammo for an easy dozen fighter kills, or an easy 8 or so bomber kills- if you hit what your shooting at... This is where having enough fuel plays in...
I've found that by working on my Hit%, everything else improves as well. But focusing on any other single aspect doesn't do that, at least for me.