My office is located in the Center for Teaching, which is on the third (top) floor of 1114 19th Avenue South. See these directions. The ROTC is on the ground floor, if that helps.
You're welcome to contact me via email (email@example.com). I'm also on Twitter (@derekbruff) and Google+. You can call me at 615-322-7290 (2-7290 on campus), but I don't check my voice mail as often as I check email, Twitter, and G+.
Image: “Telephone,” Nick Southall, Flickr (CC) - That's what phones used to look like.