Actually, changing your name is pretty easy, and you can do so very informally if you choose. An adult is actually allowed to use whatever name they wish, so long as their choice is not made and used to commit fraud. So, one way would be to just start using your married name.
In practice, this is becoming harder to do effectively, because, among other things, banks and credit-card issuers can be pretty stuffy. So, if you are an adult with significant worldly financial and other dealings, you are probably better off to follow the statutory procedure set forth in Code of Civil Procedure sections 1275 to 1279.5.
Nolo Press has a short squib on how to do this at http://www.nolo.com/legal-encyclopedia/article-30079.html and also a book that spells it out in detail.
