Pitching stories to journalists is the bread and butter behind any successful PR.  It isn't easy, and can be as frustrating for the PR pitching the story as it is for the journalist whose email in box is already over-flowing and with a phone that rings incessantly 

Jeremy Vine producer Tim Johns offers to very helpful top tips in this article for PR Week. 

I would add the following. 

1. Pick your time.  There are certain points in the day and week when journalists will not want to hear from you, and times when it is best to pitch.  Take some time to find out the best time. 

2. Don't blanket pitch. A generic pitch to multiple titles will almost always fail.

3. And sometimes say no to your client.  Some ideas should never the office at all.  PRs should be more honest with their clients and occasionally tell them that an idea is awful.