Solidify your idea until you can tell anyone what your show is about. Never ever stutter or stammer when you are explaining what you would like to film. Know your concept back and front.
Make sure your idea is being pitched to the right network and audience. Research what each network runs on air. This will save you a lot of time and embarrassment.
Present yourself well. Do not show up to your scheduled meeting looking like you just woke up. Dress for success because, after all, you only have one shot at your dream with big time producers.
Bring visuals with you, such as a storyboard. Remember that the end product of what you have written is going to be in a visual medium.
Thank your listeners for their time. Even if you think you floored them with your presentation, chances are they would never show it. Therefore, be professional by thanking them, shaking their hands and following up. If you don't hear from them, call. Make them aware that you are fully committed to your concept.