Minor things can be the best things to bring up, because they point to something specific and probably not so obvious that's a problem for you. My T is always really receptive when I tell him about things he did that bothered me. Plus I have trouble being open about other stuff if I'm holding something back, so it's better to get it out of the way. My advice would be to just say it directly. "It bothered me when you ______."

I don't exchange emails with my T but sometimes I write things out beforehand. It helps me think about exactly what I'm going to say and why I want to say it.