If you want a simple answer, then figure out what you want (fun, challenge, K/D ratio). If you want fun, fly with a squad. If you want challenge, don't worry about getting shot down. Take off from capped fields in a good (or for more challenge, early war) furballer and try to last as long as you can. If you want K/D ratio, pick an energy fighter, climb to 20k, and drop on people going to/from battles.
If you want a more academic answer, then it requires lots and lots of study and practice. You have to a) learn how to fly with skill and precision (no ham fisting), b) learn aerodynamics and how it affects the aircraft, c) learn the difference between energy and angles fighting and why some planes are better at one versus another, d) learn BFM manuevers or how to manage the geometry (position, aspect, and distance) and closure rates of a fight, e) learn ACM or how to fight more than just one airplane.
Military pilots train continuously throughout their career. Aside from a couple of years of initial pilot training, there's a 3 or 4 month long advanced fighter weapons school that is a very intense form of training dedicated to teaching the art of air combat. I have been attempting to recreate this for Aces High from scratch and will open it up when I'm ready, but it's not going to be a quick "good enough" kind of school. It will cover Advanced Handling Characteristics, detailed aircraft performance determination and evaluation (Energy Maneuverability Theory), Formations, 1v1 BFM, 2v1, 1v2, 4v4 ACM, and ACT. Varying levels of graduates will be available so you don't have to go through everything if you don't want to. If that kind of training appeals to you, great, but you'll have to wait a bit. I'm about 60 pages into a training syllabus and I haven't yet started BFM, ACM, or ACT yet. I need to get some test students through it first and I'll probably need to spin up 1 or 2 additional IPs to work with students and play the role of aggressors.