To be common law married (called Informal Marriage in Texas): 1) must agree to be married, 2) have lived together as husband wife for some time, 3) represented to other people that you are husband and wife.
You can petition to change your name as well.
Call a local family law attorney who can better explain.
BEST ANSWER I got.... and I HOPE I WAS HELPFUL!! Steve Hamer answers questions on Avvo for general information and not as legal advice. Those answers do not establish an attorney/client relationship. If you would like my help, contact Mr. Hamer at (214) 843-1529 for a FREE CONSULTATION.
If you want your common law marriage recognized, you should go to the nearest justice of the peace court in your county and fill out a Declaration and Registration of an Informal Marriage. It is a form you can also download from Texas Vital Statistics http://www.dshs.state.tx.us/vs/field/vsforms/localforms.shtm. It is form VS-180.1. You still have to take it to the county clerk to register it. Mr Hamer did a good job at laying out the requirements for a common law marriage.
Legal disclaimer: My answers are only intended as general legal advice based on my experience. They are not intended to be a binding legal opinion nor to create an attorney-client relationship.