For me it was pair programming, without a doubt. A year and a half ago I moved from a large enterprise to a small consultancy who practices pair programming. I

For me it was pair programming, without a doubt. A year and a half ago I moved from a large enterprise to a small consultancy who practices pair programming. I've learned a great deal more in that year and a half than in the preceding five years working solo on agile and not-so-agile teams. Good practices and spending time attacking problems together with various colleagues across different projects and tech stacks is what has gotten me to that next level. I'm completely sold on the practice. I'm much more productive while working with a partner than I am solo as well.