If you are an OSM activist invited to participate in a TV show to present OSM, you might find the following ideas useful.
Please note these are ideas and you don have to present/use all of them.
Material and ideas
It is most likely that animations and such imagery is hugely useful to make an impression on the viewers. Try to focus on the area/country you are in, if you can make an animation for that area, that is also a HUGE leap.
Don't forget: Sell the benefits, not the features!
Animations and videos
- ito's "OSM 2008: A Year of Edits" - it is CC-BY-SA, so there is no license issue, as long as ito is credited (make sure the last frame is shown to stay legal)
- try to produce an animation of the area you're in or the area that is the target audience
- example Galați, Romania
- if there are areas with huge progress, activity or interest, focus on those in the animation
- show the applications (routing, maps, 3D visualisation)
- use maps.cloudmade.com to show the huge routes:
- Blindpeople's OSM
- OSM 3D (for now just Germany) - see Video page
- public transport maps: , , , 
Read Writing_a_press_release and be sure to be aware of the caveats, in a sense you are making a press release.
Issues and ideas that you might find useful to bring up:
- Very short history of the project and motivations behind it; it grew to be world wide available
- Commercial geo data has artificially-introduced errors
- History of the participation in your area (if known)
- Usually information doesn't lose its value if more people know about it, so is natural that spreading it is almost cost free; usually, more people knowing about it increases its value through contribution
- Very fast availability - examples (in Bucharest bridge Semănătoarea was closed and only a couple of days later OSM was showing the change)
- Advantages of having the data
- green areas per capita
- air quality prognosis 
- road network statistics (paved/non-paved ratio in different areas)
- new products
- fast updates
- unconventional usage (e.g.: maps for the blind, MTB, and sky tracks)
- complex routing algorithms are possible (combining train, bus, bicyle and walking)
- applications in mobile devices
- garmin maps
- navit - preferably with a small device such as a phone
- filtering and finding amenities (e.g. ATMs, restaurants, fuel stations)
- Professional or research usage of OSM data (since there are standards such as WMS)
- contributions from public institutions - Netherlands, USA, Bavaria (Germany)
- Scholar Research
- Garmin usage and availability of data (in contrast to yearly updates of commercial offers, we have or can have daily updates)
- This is not limited only to streets, see:
- mapping parties (example from your area, if any) and the results
Don't forget to say: "Go to www.openstreetmap.org to see the map!"
Contributing to OpenStreetMap is possible even without a GPS unit:
- mapping over aerial imagery (Yahoo imagery and others)
- adding POIs
- adding the public transportation system
- contributing code
- importing publicly available data
- getting agreement from public officials to use public data sources (e.g.: city maps which the city owns copyright of) in OSM
- mapping by using already imported GPS traces (e.g. norc.ro donated traces)
- obtain traces from taxi drivers and import them in OSM (might need anonymity, and OSM offers this possibility without special effort)
Contributing when a GPS module is available is easy:
- making traces, uploading them and mapping
- taxi drivers
- sport activities can be tracked (skying, hiking, rafting)
- mapping parties (other people might provide spare GPS units)
See the Getting Involved page about other ways to help the project.
Don't forget to thank
You shouldn't forget to thank the people who invited you, those who helped you and keep a door open for possible future invitations ;-) .