Well, there's a lot of ways you could go. You could specialize in specific illnesses. The big ones are Bipolar, AD(H)D, and Autism. You could also specialize in a certain age group. Infancy and pre-adolescence is big if you're looking for helping more family situations and coping with what will be life-long struggles (again, Autism will pop up here a lot...as will the children being in a family where mental illness is prevalent). Adolescence and teenage years are going to be where you will address possible misdiagnoses as well as the "surprise, you're crazy" moments when the first episodes of the bigger illnesses start to show up (i.e. bipolar/schizophrenia/etc). You could also specialize in ethnic or socio-economic groups. This is big on if you're addressing issues that society has had more of a hand in, like PTSD dealing with abuse, or the foster care/adoption system.