The law allows an individual (NOT a corporation) to represent themselves, but it is not recommended. You are termed a "pro se" party in that event. As to representing yourself in criminal cases, that will not be discussed here since it is an inherently foolhardy thing to do and requires specific procedures in front of the judge in order to request to do so.
As to representing yourself in civil or family matters, please understand that you will be required to follow all of the same rules of procedure, discovery and evidence as is required for attorneys. Further, the judge cannot give you any advice or help.
There are resources on the internet and in libraries of which you might want to avail yourself, especially in divorce and custody matters. A couple of links to websites follow which many judges would prefer for you to use if you are going to represent yourself in a divorce. However, no advice can be given about the proper way to fill out the forms.
Pro Se Divorce Handbook, The Texas Young Lawyers Association (TYLA) And The State Bar of Texas, 2010
Divorce forms from the Texas Young Lawyers Association (with and without children)
The TYLA also has forms for a few other areas of the law.
Divorce forms from the Travis County Bar Association, Family Law Section, and the Travis County Domestic Relations Office. NOTE that much of the information from this source is specific to Travis County, but there is a great amount of general information as well and the forms are useful.