Audio.

I'll go the videogame angle though: I am pretty confident in my Quake3Arena/QuakeLive skills.

Its a pretty complex game when you get down to it. Duelling plays a lot like a board game. The game is more about resource control, power-ups are timed and you can have an entire metagame based on timing when the power-ups respawn and how you decide to position yourself on the map relative to location and resources. Of course, you should have all of the maps memorized and readily accessible in your mind visually.

I always like to show this video that has Rapha doing a complete run-through of his victory match:

http://www.youtube.com/watch?v=XdkDjsBiO58

However, before you even duel you should have all the elements of Quake already mastered. From dead-accurate rail shots (you can mostly kill someone with one shot, but you have to worry about the recharge penalty which leaves you vulnerable) to rocket jumping, strafe jumping, dodging (if you have ten rockets sprayed at you, can you avoid every single one?), to everything in between.