Where can I find out about graduate school admission in general?

There is lots of information out there. Speak to psychology professors at your undrgraduate institution and get their recommendations. If you have a well-focused research interest, read lots of current literature in the area. This will not only inform you about your field, but will give you an idea of who the principle researchers are in that field. It makes sense to apply to schools where those researchers are on the faculty. 

The APA publishes a book that may be helpful: Getting In: A Step-by-Step Plan for Gaining Admission to Graduate School in Psychology.