When the wind comes across the boats on opposite sides, the boat with the wind on the left (port) side must give way to the boat with the wind on the right (starboard) side.
When the wind comes across the boats on the same side and they are not overlapped, the boat behind (clear astern) must keep clear of the boat (clear) ahead.
When the wind comes across the boats on the same side and they are overlapped, the boat on the windward (upwind) side must keep clear of the other leeward (downwind) boat.
Umpires follow each race and make instant penalty decisions. A green and white flag means no penalty but a yellow or blue flag means the boat in the match with the corresponding flag flying on the back of their boat must take a penalty before finishing. A penalty turn when sailing towards the wind means turning the stern of the boat through the wind and when sailing away from the wind a penalty is taken when the boat turns the bow through the wind.
Visit Appendix C of the ISAF's Racing Rules of Sailing to view the rules for match-racing.
Racing Rules Changes
AWMRT Call Book
The start is critical
The end of the first windward leg provides an opportunity for the trailing boat to seize the edge by trying to create an inside overlap at the mark, forcing the leader to give room which usually means relinquishing their lead.
Dropping the Spinnaker
To the Finish