HRE Nobility titles and how to Address them

In the Holy Roman Empire, how were Barons, Counts, and Dukes addressed by commoners or fellow lords?

Additionally, how did they interact with one another? Would barons meet with the count who gave them their land often? Would they be expected to participate in their count's or duke's wars?

Finally, what role did villages and towns play in this? Would a Baron be in charge of a couple of villages and then a count of many sets of villages held by other Barons?