ORD was my first taxi out as an airline pilot. Dude, talk about a wake up call. Luckily I had a good captain who looked at me right before I called for clearance and said "wait, this is your first time ever taxing a commercial aircraft?" "Yep" "Ok, write this down" and proceeded to give me what he expected the taxi instructions to be. He was 95% correct and a huge help. He also said 'don't be surprised if they read off your taxi instructions and then go on to the next airplane without giving you a chance to read back'. I think I said "WTF, can they do that?" "This is Chicago, FAA regs are more like suggestions..."