It will depend on your nationality, since many Embassies may have slightly different requirements.  So, it will be wise to contact your Embassy and ask them what sort of documentation will be required for you to bring in order to register your marriage in China.  Also ask if you will need a prior appointment, or just show up at your convenience. 

Usually, your embassy or consulate provides information on the process to follow to officially register your wedding. As, each country has different rules and procedures, like HappyExPat, I advise you to contact your embassy/consulate directly.

To avoid any problem, make sure you get all the proper documents before you actually get married, as your embassy/consulate may ask your foreign/Chinese wife to provide documents that cannot be issued once she is married.

Is this the same idiot who posts all the ambiguous questions refering to a non-specific nation? NOT ALL COUNTRIES ARE THE SAME.  

It would be more important to note the Chinese will need different documents depending on where the woman is from. Not only are the embassies requirements different depending on your nationality but the differences between what province and capital city the girl comes from. All in all, it's not that difficult, I would have the future wife call the marriage license office to find out their requirements first then find out from your embassy. Most of the time the license office will be able to tell you exactly what needs to be done even with your embassy

I just did this in May.  It depends on your country's procedures.  Usually a visit to your country's embassy's website will answer most of your questions.  You may have to email them.  Really, it can be as easy as filling out a form and having your marriage book translated into English or the mother tongue of your country.  

In the USA, if you file a joint tax return, then you are automatically married.  Common law in the USA supports verbal confession of marriage as a valid marriage.  If both people agree they are married, then the court has no problem recognizing that you are married as long as it doesn't hinder the rights of a third party.  Of course, this is between a man and a woman.  Not the case in homosexual relationships.  Common law permits, If it looks like a duck, walks like a duck and talks like a duck, then it is a duck.  Technically marriage is a contractual agreement between a man and a woman.  Verbal contracts are valid as long as there is no dispute between the contracting parties.