(1) Switch the radio to high power mode before transmitting.
(2)Prefix your boat name with "Sailing canoe" so that people know what nature of vessel is in trouble.
(3) If you are using a working channel to talk to other boats in the group (we used Ch 6 in the Luing meet), make sure that you switch to Ch16 before making your distress or urgency call, otherwise it's very unlikely to be heard by the Coastguard or other vessels.
(4) It would be helpful to have some idea of your position, even if sailing in a group and delegating all navigation to group leaders, otherwise you'll be unable to guide rescuers to you. Of course sailing in a group means that someone else in the group could call a Mayday on your behalf.
(5) It is prudent to make radio checks within the group and with the coastguard.
(6) An information card to laminate and keep with your radio is available from the Files section of my web-site.