The first time around I applied to 5 programs at 4 schools. Now that I've finished my masters, I have a much clearer idea of what I am looking for in a PhD, so I only applied to the program that really fit my intellectual interests and finances.
I would recommend that you apply to as many programs as you an where the program, research, etc. match what you are looking for and where you can craft really good applications (don't let your SOPs suffer bc you're applying to too many schools).