I knew a guy in college who got to do this for the Sixers one year. He got to sit relatively court-side and just had to keep an key on the game and write down everything. He used pen and pad, but I would imagine that capturing that data is a lot easier today.

I was looking at espn's feed of the game the other night and they seem to have a lot of details about the game as the game is being played. things like "player missed 13 foot jump shot" and a graphic of a ball bouncing off of the rim and where it was shot from. Id imagine that they have a system like court stenographers so that they can quickly record info and send it to their servers.