I'm entirely self-taught and I tend to stick to 'white' key signatures and have no problem in the keys of C, D, E, F, G and A.

Okay, so I know that changes in many songs require that some parts of the song be in other keys (intros, bridges, etc.) and I manage that okay as well, but rarely, if ever, do I start a song in one of the 'black' key signatures.

Now I'm not sure how this works, but a friend of mine, also self-taught, prefers to play in "black" keys: C#, Eb, F#, etc.