Hi Joel,
My recommendation would be to observe how the other teachers at school interact with the students and follow their lead. Also ask your mentor teacher if he/she thinks your interaction is appropriate - that is allowing the students to be too chummy...
It's even difficult at the college level because in my EDUC 401 class, I really like my students and want to be friendly...but have to draw the line in also requiring good work from them.
Kaye :-)