I think it's important to establish a relationship with the teacher right away, so if problems do arise she/he will know that I am approachable.
Every person has their own favorite method of communicating, so I ask the teacher "what's the best way to reach you?" and go from there. When I was teaching preschool I preferred NOT to do email because if we had a problem arise, I wanted them to be able to talk to me about it in real time. I have found that when there is a problem to be addressed, for many people, email is susceptible to misunderstandings. Esp for parents of younger kids, when their children are not as skilled in retelling events from their day. I would rather have a parent call than sit around all night wondering if I got their email or worrying about a situation.
That said, I also know that many teachers do prefer email, and so if something arises, I try very much to ask an open ended question like "Kiddo said such and such happened in class and I was hoping you could tell me more about this." I recently emailed the teacher because Kiddo was fretting over one part of his regular school day and since he does have some challenges, I wanted to clarify if this was him just griping or if there is something which he was needing more support on. It turned out to be the latter and she was able to provide me with a few tools to help.
If I believe there is a problem in the classroom around the behavior of another child, then I might ask "Kiddo has been pretty upset because another child has been doing X to him; I was wondering if you had any tools for your classroom in helping the kids to stand up for themselves". Here, I'm putting the responsibility of Kiddo standing up for himself on him, and also alerting the teacher to a problem. I want to be sure to address situations from a perspective of 'how can we help Kiddo cope with this/mature' instead of "that kid over there is doing XYZ..." The interesting thing is that once the teacher gets that sort of information, they are likely to make an effort to notice what's going on between those two children and to observe what the problem may be. It also allows the teacher to address the issue without having to deal with a parents who is saying "what are you going to do about that little so-and-so who's being mean to my kid?"
It sounds like you are on the right track with being responsive, giving positive feedback and making yourself approachable, K-Bell. Good for you. :)