Commuting time, airport delays, lunch, breakfast in bed are all opportunities to read something new.
Read newspapers that are at odds with your political/intellectual leanings; your audience is diverse and, whether you sympathise with their politics or not, you need to know what concerns them. Being confronted with things you don’t understand or agree with is a great way to trick your mind into coming up with new ideas.
IIf you hate the idea of celebrity, dip into Heat Magazine occasionally – your take on the subject will be different to someone who is immersed in that world.
If you see a chance to secure unique access to a person or a story, move fast – there will be lots of people with the same thought.
Other ways to generate new factual TV ideas:
Get more development and pitching tips in Greenlit: Developing Factual/Reality TV Ideas From Concept to Pitch