You need some formal qualification in journalism or media studies to start anywhere. Many print journalists do a qualification called NCTJ. You'll need to get some basic experience on a weekly paper, local radio station or you might be lucky and bag a traineeship on a national, or for the BBC and ITV. It's quite hard to get into, and lots of people start out reading the news of Capital FM or one of the smaller London radio stations. Some people manage to cross from print journalism into TV very smoothly but however you get there, you'll have to cut your teeth on somthing fairly humble to start with