As the other agent mentioned, research on-line with the Houston Better Business Bureau as well as other sites. You will likely find good and bad on-line, but a good place to start.
I always want my buyers to speak to neighbors as well as drive around and see how all the builders are doing. If one builder is selling more homes than another, there is likely a reason.
Most builders offer incentives to build, but are not going to negotiate a off their base price. However, if they have a home already built with no buyers on it, that home might have incentives or some room to come off the price. Again, you have to review inventory and upgrades in the home and see if any have sold recently as resales in our MLS to compare.
As you can see, having your own agent will help you. You do NOT pay their commissions...so hire an experienced Realtor to help you before you get serious in speaking with a builder. I just assisted a buyer who found me here on Trulia. I saved them $13,000 with building with another builder they did not know on a larger lot. You just need someone that knows the area.