For lunch try the "Business Lunch" at The Palm. Relatively inexpensive, good food especially if you like steak. Yum.
If you feel like spending more and have 2 hours to completely waste at lunch try Charlie Palmers' at The Joule hotel downtown. Good food, cool atmosphere.... don't be too hungry and don't be in a hurry, be prepared to spend too much.
Try Stephen Pyles downtown for dinner. Expensive, very. Worth it.
One night go to Strokers and have a Blues Brothers Burger (if you like blue cheese) and beer.... if you like motorcycle people that is.
If you want to get a little out of mainstream, look up a place in South Dallas called "Bishop Arts District". Go to Bolsa for happy hour and dinner.
http://www.bolsadallas.com
Just depends on your price range really, Dallas has some damn spendy places and some bargains.
If someone were coming to Dallas and asked me for 2 places for dinner I'd send them to Bolsa one night and Strokers the other. 2 completely different worlds.
The others are good but sort of fru fru.
Dislclaimer: These are actual Dallas, meaning downtown and close to it. If by Dallas you really mean way the hell up north then it's your standard chain garbage and you're better off finding an In-N-Out.
Or, the best thing you could do is go to Ft. Worth
Good luck!