There's been some good advice already, and I'll add my 2¢:
  • Find a builder you trust -- this is the hardest part, since most are not completely trustworthy. My guess is you are looking at a sub-division (like Grayhawk) with several "big name" builders. Check them out. Look at the houses in progress in the neighborhood, and see the level of workmanship. Talk to people who own that builder's homes (I'll be glad to give you my impressions/opinions about Legacy/Meritage).
    Find a location you like. You are going to live in this community a long time, make sure you like the area. The community's amenities. The community's covenants. The stores in the area. The traffic (no traffic in DFW is "good", but you'd better make sure the 5:00 rush hour is something you can live with). The schools (if you are planning to have children). This is stuff you can't change, so make sure your OK with it.
    Pick a floorplan than is what you'll need... in 5 to 7 years. The last house I bought was perfect for us the day we move in, and it was twice as big as our previous place. We figured we'd never outgrow it. 2 years later, we were wishing we had bought something bigger. We ended up selling it -- for a small gain -- to buy our current house after having lived in it less than 5 years. We could have saved ourselves a lot of trouble if we had though ahead a little more. But the reverse can also be true. My boss spent 2 years building a custom designed, custom built 8,000 square foot house. He moved in 18 months ago, and it's now on the market... he says it's too much house for he and his wife.
    Once you pick a floorplan, put in the options that you can't easily add later. Sure, wood floors are nice. But those can be put in without much trouble 5 years from now. But optioning that downstairs half-bath with a shower (to make it a full bath for your guests) would be much more expensive after the house is completed. $3,000 might sound like a lot of money to add 4 or 5 feet on to your garage's depth, but doing it now will be a lot cheaper than later. Save the carpet upgrades for later... they can wait.
Well, those are my "words of wisdom", for what they are worth.