Hi, I'm mcpower. I've done Advent of Code seriously for two years now in Python, placing 9th in 2018 and 12th in 2017. This year, I'm taking a break from aiming for the leaderboard - while it's fun and all, it is a bit stressful at times (the good kind of stress, though!). As such, I'd like to share a few tips for anyone wanting to aim for the leaderboard.
This is everything that worked for me. Your mileage may vary, though - don't take this as gospel, see what works for you.