For me its about two things:
1. Pattern recognition: this is what my brain does automatically, for example i place my L piece on the right side of the field and my reversed L piece on the left side of the field in like 80% of the times. I caught myself doing this a lot(with all the pieces and combinations) and that makes me play fast cause i make decisions faster but the problem about this is that once you learn yourself this pattern you get stuck with it and its not always the best pattern so learning it otherwise is hard. This is why i think some ppl are fast but not as good as other slower people.
2. Piece placement: Just being able to place the piece on the spot you want. To me this just came with time, there was a time my brain was faster then i was able to place it and now its other way around :-)