See: handgunlaw.us
Where are you traveling to?
If you are crossing a state line, then a Federal law applies. In general, it means that if the gun is legal at the end points, then you may transport it through states where it may be unlawful. "Unlawful" can mean anything from the ammo, gun, magazine, part, or some sort of ownership permit.
The means in which you transport your gun is very important. In general, you must (applies to Texas, but check the code for rules on transporting firearms):
1) Separate the gun from the ammunition. There is some variance in state laws on this. Therefore, do NOT load any magazines. Put all the ammo in a different LOCKED container.
2) Lock up the Glock using the lock that came with it. Put it in a case or some sort of lockable box. Put the magazines with the Glock, not the ammo.
3) Place everything in the trunk of your vehicle or in the back seat. It needs to be "out of reach".
Remember, if everything is locked, they cannot do anything to you IF the gun is legal at the endpoints. Also be aware that though Federal law protects you, some states such as New York DO NOT CARE and will charge you with a crime anyway.
I believe the above should be more than sufficient for driving around Texas. However, check the code. It should be online.
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Additionally, do NOT answer any questions from law enforcement. Do not state you have a weapon in the car. You do not need to answer, but you need to be smart about it. If you are stopped, simply ask "What is this about officer?" Under no circumstances should you give them permission to search. The trick is to be firm while being polite. If you get the old "But if you have nothing to hide..." argument, just smile and say "Thank you officer for your concern, but we both know reasonable articulable suspicion doesn't work like that."
If the gun is locked up in a container, they cannot search it without probable cause that a crime has been, is about to, or is being committed.
You really need to do some research into how to handle the police. Check out You and the Police! and other sources especially if you don't know what "reasonable articulable suspicion" and "probable cause" are.