If a cyclist passes me without warning me that they are passing me, I yell out loud, "Signal that you are passing me, please". Some yell, "Passing on your left", after they hear my plea and some just give me the look like I am way out of line.
If you are out driving, whether you are driving your car or your bicycle, please be courteous to other vehicles and users of the path/road. If you are doing this already, great! Now, let's please get the word out to others as well. Just my 2 cents!!