Hi.

I'm wondering if any of you guys know if something needs to be done with video footage before it goes for broadcast on TV.

I'm just about to go into the color correction phase of my project. I have some experience from this - that is - balancing the color and tone of the images just so that it suits my eyes.
But do I need to check any gamma and black levels? I heard that some TV stations don't accept overexposed video cause it screws up their equipment? Do I need to clip high and low? Or anything else?

You'll probably need to legalize the footage. This makes sure that the reds are not to red, the whites not to white etc...

The best guide is to ask the network or cable operator if they have a Contributor Guide. Like the Red Book that the Public Broadcasting Network has here in the U.S.

Fundamentally, as has been stated, you have to adjust your video to meet the signal standards set for your country and video standard. You are normally expected to manage the audio as well and deliver the video with very specific timing so they can manage station breaks and commercials. They may also expect you to create the equivalent of a film leader, called a Slate in which you give the details of the program that follows.