Struggles n' Such

I suppose something that is puzzling/worrying to me has less to do with ideology and more to do with implementation of those ideas in the classroom. What current scholarship seems to be pointing to is the necessity of different and innovative approaches that match the changing needs of a diverse student body. Teachers and professors who are able to tailor their methods to individual classes, students, or situations are much more likely to have "success in the classroom" than ones who rely on the same structure they have used for X number of years. In thoughtspace, this all sounds well and good, but how do you, as a teacher, identify where students are coming from? How do you decide what method will work best for each class, and how do you work with the individual students who need such tailored approaches? I'm sure that this sort of knowledge will come readily with experience in the classroom, but I suppose that I, like many people who want to teach but have only limited experience, am deathly afraid of failing my students (in the sense that I fail to teach them something, not that they fail to pass the standard assessment measures).