One that is hard to miss is the fact that we bow to the masters of our style to mark the beginning and ending of class. This is showing respect for all karate instructors, the art we are learning, and the people who have helped pass it down to us. In Okinawa and many other places, bowing is simply a show of respect. The closest equivalents we have in the west would be shaking hands or a military salute.
A karate-ka is expected to bow when they approach/address a senior karate-ka (especially a black belt). This again, is a sign of respect. The senior karate-ka will almost always return the bow as a sign of mutual respect.
When entering/exiting the dojo floor, a student is expected to bow to the room. In karate we show respect for everyone and everything. A dojo is a very special place to a karate-ka. Showing respect for the room is also done in other ways. For example, after class it is tradition to help clean up the dojo in various ways. One may think this is just a way to get the dojo clean, but it also teaches lessons about responsibility, respect, and ownership. Unfortunately this tradition can't always be followed at our YMCA branches because it wouldn't be fair to ask students to clean a gymnasium or all-purpose-room when most of the mess wasn't caused by the karate class. Other ways to practice this would be to help your Sensei collect targets and equipment, or to make sure the practice floor is clear of debris before class starts.