1. Observe rules of the road when converging.
From:
http://dbw.ca.gov/Pubs/Windsurf/
The guy that is circled has the right of way. That is the guy on your "RIGHT HAND FORWARD SIDE OR THAT YOU ARE GOING TO PASS."
2. If you are meeting head on with another person on the water, remove any doubt well in advance of meeting by holding your arm up above your body and pointing in the direction you are going to travel in. This simple courtesy will avoid some hard feelings and incidents.
3. Pass well upwind of others to where you lines and kite never come close to them. If you come too close why not stop, park your kite at the vertical while well offshore and wait for the situation to pass in moderate winds?
4. Incoming riders should ideally yield the right of way to outgoing riders.
5. Don't jump upwind of others on the water inside of 300 ft., ideally.
If you have guys that ignore all of this routinely you need to have an effective talk with them. Saying it is too much trouble or they won't respond before trying is as good as voting to cause incidents and possibly accidents and loss of access.
The IKO also has a good illustrated guide to the Rules Of the Road at:
http://www.ikorg.com/priority_rules.php?menu_id=2