Try your best to juggle the soldier in the spawn doors
Learn to count your enemies ammo and health
Learn to quickswitch between your rockets and sg to optimize dps
Make it easy for your medic to arrow you, the heals usually give you a net gain of health even if you get hit
Don't forget that you're playing KOTH and that maximising cap time is key - often kiting the other soldier and wasting time is a good play
Count your ubers closely, a small uber ad can be really powerful on small maps
People who dislike the gamemode 99% of the time don't understand how to play it, outplaying your opponent is definitely possible and there really is a lot to learn.