How to approach an engineer?

If you need to talk to your co-worker who happens to be an engineer, then never (i mean never) go and tap him/her to start the conversation. It will freak him out. And in case he is listening to some music with his headphones on (which is true 90% case) then tapping him may make him fall from his chair. So don't do it. If you want to talk.. then send an im first. That the best practiced approach. Thats the general norm. :D