The limit in Texas is 12 per day, two days in possession (24 birds). If you're huntng on opening day and you have 24 birds in possession you're in trouble. If you're hunting on the second day or any day thereafter it'd be hard (not impossible) to prove you didn't get all 24 in one day. If you are carrying birds for someone else, the bag holding the birds must be marked with the other hunters license number and you must have a signed note from that hunter stating you have permission to carry the extra birds.
Couple of things more about dove hunting in Texas. There is a special white wing zone along the Texas/Mexico border. That zone opens around the first part of September for two weekends. Hunting in that zone starts at noon - you can not hunt in the special white wing zone in the morning.
The gun must have a three shell plug for hunting dove in Texas. You can not shoot five shots (or more) at one time during dove hunting season.
I hunt with a couple of fellers that use the one shot one bird rule (I hate em). Me? My philosphy is if you throw up enough lead in the air something is bound to fly into it. I'm usually a one case, one bird man.