After the research I've done in the internet I was convinced the best time to book your wedding photographer/videographer is at least 8 months before the wedding. Last week I've learned that it is far to late! Photographers are currently booking into 2014! In fact, it's the best to book it as soon as you know your wedding date.
I thought that maybe we all could exchange this kind of little tips that we've learned in practice here on this forum to help each other avoid bad surprises.