Here you can find the zones (different parts of the state have different seasons, but it's not as complicated as county-by-county deer)https://tpwd.texas.gov/regulations/outdoor-annual/regs/animals/duck
You can also find the bag limits, they're kind of complicated for ducks, in general you can usually shoot up to 6 a day, if you have the right species coming to your decoys. There isn't a season limit like deer.
Right now, because we've passed "the split" in all zones, statewide is open until Jan 28.
You have to stop shooting at SUNSET, not 30 minutes after like deer. You can shoot 30 minutes before sunrise.
Get steel shotgun shells in 2, 3, or 4 shot size.
You need to be HIP certified (free) and you need a federal duck stamp on your license (not free). You can get all that online at TPWD.
You're probably better off going with an experienced hunter your first time if you can get them on your property, because of the complicated bag limits. Also because they'll have the decoys, etc and know how to hide and when to shoot.