I get this question all the time.
The moment you turn 18 on your birthday you are free to leave. You leave with the clothes on your back. You can only take things that belong to you - gifts, things you paid for (have the receipt) and things that your parents let you take. If they say no, then the item stays.
You are free to call your local policing agency (police, constable or sheriff) and talk to them about their policies. Normally they will escort you off the property but they don't have the time or manpower to watch you load up your vehicle with "stuff".
So if your parents bought you a bed, a computer, phone, etc., it belongs to them unless they allow you to take it.
You can attempt to emancipate at 16 or 17. (If you are under 16 then you are just plain out of luck). Judges don't like to do this. It is very expensive. I would estimate the cost to be at least $5,000 or more. And it does not mean the judge will sign the paperwork. For example, I require a $10,000 deposit to begin this process - that stops most teenagers because they would rather buy a car then spend money on an attorney that might not be successful.
I don't understand what teen-agers hope to do by emancipating. Most apartments won't lease to you since you won't have a credit rating. You probably don't have a bank account. If you have a job, odds are it low paying and landlords expect you to show that you can afford to pay the rent.
The only teen-agers to emancipate in the Houston area are usually sports figures and/or musicians. They need to be able to sign legal contracts (which you cannot do until you are 18 or emancipated) for endorsement deals. Even then, the judge makes everyone jump through lots of hoops.
To merely file a new lawsuit (emancipation is a lawsuit) is around $300 to the county clerk where you live.
If you have a friend or family member that is going to let you live with them that is NOT enough to emancipate. You must be 100% self-supporting without anyone else's help.
Emancipation is called "removal of disabilities" in Texas. The Texas Family Code is available on-line for free. Read about removing disabilities if you are interested in researching this matter.
If your parents are willing to let you move in with another family or person, that person should be an authorization by a notarized document to register you in school and take you to the doctor. It also avoids having the police show up and threaten to arrest the person for having you in their home.
If I was the person letting you move in, I would not let you move in until I had met with an attorney in person and made sure that I had your parent's permission to allow you into my home. Quite frankly, it's just not worth the risk or possible hassle with policing agencies.
Yes in Texas after the age of 12 you can meet with a judge and tell the judge who you want to live with but the judge is NOT bound by your wishes. The judge determines what is in the child's "best interests". The term "best interests" is not defined in the Texas Family Code.
If you are unhappy, talk to your school counselor, religious leader, or a medical provider. If you are in danger they are required by Texas law to report it to the authorities.
Beware of making unfounded allegations since it opens the door to CPS. And, since most families don't want teen-agers in Texas there are "facilities" for teen-agers to live until they turn 18. Most are in small towns (so if you are in Dallas or Houston the odds are that you won't be housed in your town) and it's not a prison -- but it has no "frills". The kids I've known that got sent to one of these places tend to later claim that no abuse occurred in order to try to escape from these places. Plus, the other kids there are usually in crisis mode too and many come from horribly disfunctional and even violent homes. Some of these kids don't talk - they just like to fight. And many of these kids have been in CPS custody their entire lives and don't like newcomers showing up.
If your situation is dangerous, then make outcry to a medical care provider or school employee. Again, they are required by law to report it. You can also call 911 or CPS yourself.
In closing, the good news is that you will soon be 18 and you can make decisions for yourself. We've all been teen-agers and it's a period of my life that I would never want to re-live. It sucked - but I did survive it. And if you are smart, you will survive these teen-age years.