The best way to look for a job in emergency medicine is to decide the geographic area in which you want to live, then contact all of the hospitals/groups in the area and find out about any current or anticipated openings. This also puts your name on the list of people they would contact if an unanticipated opening occurs.
Other postings that say that oftentimes the best positions are not advertised are correct, and if you don't have any word-of-mouth connections, then the only way to get one of these jobs is to contact the group on your own.
At the risk of being labelled a spammer, I created a directory at emergencymedicinedirectory.com to help graduating residents with their job search by providing a list of hospitals and who staffs them. Oftentimes finding this information on your own is extremely time-consuming, I know that it was when I went through my own job search 5 years ago, and then again this past year. I've tried to make the price of the directories extremely reasonable for graduating residents, just enough to cover the cost of creating the directories. It's just another tool to help you find the right job for you.