I gave the answer 'myself' earlier in this thread, and that is very true. But there are actually only two people in this community I'd like to thank, but even they had limited roles in teaching me how to play. They acted more as catalysts to speed up, rather than expand my knowledge.
Firstly, MariQo15. Although an insensitive bastard sometimes, a good player, and he dragged me out of the osniping days, and thought me some sniping skills before the sniper was changed. Also released a capping video on youtube that inspired me to cap. Second, the video entitled 'Full On!' by the one and only Disci, which taught me how to use contagious OD properly to chase (even though the two clips he recorded of it were not the best!), and a mechanic in the game that I wish was more used. A shoutout also goes out to MJ, who helped with a few editing tips (And the music that both me and him liked)
Other than that, no one has helped me play better. It has always been an encouragement however in pickup games to see who is scoring the best and then going out to get higher in the points list. I find the list an encouragement to see how well I'm playing, despite what position. If I'm scoring badly, I know I'm doing a *chocolate cookies* job, and look at myself to see how I can play better in that role. And usually I step my game up, helping my team more.
To be honest, I'm quite impressed with myself to reach this kind of level without any proper help or training. Hell, I never got told where the ammo boxes were, I never got told how to use the famous 'DOWNJAT', and I never played a pickup in the old IA days. I also feel that I can play any and all positions, finding it useful when I am captain, and don't get a player that I could of done with, as I can simple shuffle the team around and put myself in that required position. I find even when I'm not captain, playing a versatile amount of roles.
So therefore, everything apart from the things I have mentioned above, are completely and utterly self-taught. Which is why I said 'Myself'.