Customs is simple, just follow the signs have your bags exray and be done with it. One of my trips through Chengdu I was randomly choosen for the search of the day it seems, was not a big deal. A lot more friendly than the Psycho rentacops at LAX. Oh ya piece of advice when the US asks you what was your duration of stay, or the reason, do not give them a smart ass answer, like, umm What does my passport say? And when they ask if you are an American Citizen do not say, no I'm a walking meat puppet on a stick. But the guy was an asshole to the person in front of me so he had it coming. Then again he also looked at my drivers liscense and stated you cut your hair a few moments later, I had to commend him on his keen observation skills.
Everything in China even when my bags were searched, was very polite, they get pissy with the Chinese that do not read the signs and wait behind lines, so be good and do not follow the Chinese lead when approaching customs officers hehe ^_^