1. Waiting too long before seeking legal help.
Texas law requires that you follow certain procedures when you file for divorce, as well as if you receive notice that your spouse has filed for divorce.  There are acceptable forms you should use in filing a divorce petition, answering a petition that you have received and requesting information from the other party.  There are also certain deadlines you must meet.  Missing these deadlines can be fatal to your case. Therefore, it is crucial that you contact an attorney as soon as possible.

2. Hiding your history (or that of your spouse or your child) from your attorney.
If you file for divorce, the opposing party has the right to obtain information from you regarding your financial, criminal, parental, substance abuse, medical and psychological history.  Even if you do not give it to them voluntarily, they may be able to obtain it from other sources.  If you hide or lie about any of these issues and it is discovered by the other side, your credibility is destroyed, and it will almost certainly damage your ability to get the outcome you want in your divorce.  If you tell your attorney upfront about all prior history, he can evaluate whether or not it will be a problem for your case.  However, your attorney cannot deal with an issue about which he or she does not know.

3. Hiding assets.
The quickest way to lose the assets you are entitled to in a divorce is by trying to hide assets, debts, etc. from the other side or the court.  Most spouses have a general idea hide or lie about what assets exist in the marriage.  Also, there are other ways for the opposing side to discover any assets that you do not disclose.  You will usually get a reasonable division of assets if you are completely honest about your total financial situation.  If you lie about it, you are inviting the court punish you by giving your assets to your spouse.

4. Not working as a team with your attorney
Although the attorney is in charge of preparing the case, he or she will need your help to do so.  During the course of a divorce case, it is essential that your attorney be able to contact you and, when necessary, enlist your help in obtaining certain information and documents.  You will also need to be available to assist your attorney by answering discovery requests (formal requests for documents and other information) from the other side, preparing for depositions and preparing for court hearings.  The best attorney in the world cannot help you if you do not assist him in preparing your case. 

5. Misbehaving in court or at a deposition.
When you go to court or to a deposition the rules are simple.  Tell the truth, dress appropriately (nice, conservative clothing), be polite, do not get angry, do not answer a question that is not asked, do not argue with the judge or the opposing attorney, if you do not know the answer to a question do not guess, and do not talk over someone who is speaking.  Remember that when you go to trial, you are "Exhibit A".  If the jury or the judge does not like you and does not believe you, they will look for a way to deny you what you are requesting, and you will lose.  The way to be likable and believable is to assist your attorney in preparing ahead of time for your testimony, being completely honest at all times and being courteous to everyone involved in the case, including the opposing attorney.  If you are obnoxious or do not tell the truth in court or even at a deposition, you will damage your case.  If the judge or jury likes you and believes your story, they will usually try to find a way to help you achieve the result you want, or at least a fair result.  And, even if your case settles without a trial, being courteous and honest with the opposing side and their attorney will usually yield a better result.