Get a buddy and find a blister pack of Midland GXT (or GTX I can't remember which it is). That will put you in touch with pretty much everyone you need to talk to at an airsoft game.
Radio Etiquette
Radio channels are used to transmit vital information only.
Consistency is important! Everyone communicating the same reduces mistakes.
Listen to radio communication that may indicate special instructions needed in your area.
Keep your radio with you at all times.
Avoid stepping on other transmissions.
Avoid “keying” your microphone (PTT held down)
Normal Transmitting
Press radio key firmly, hold, pause for a second then begin speaking into the microphone. Direct your call to the person first, then announce yourself. Example: “Control…flag one.” Wait for acknowledgement “Go ahead flag one”, and then state your message.
When using a radio you must be very specific. You cannot say "I see people in the trees". We play in forests. There are lots of trees (and a lot of people). Say "I see 3 people wearing ACU pattern at the north east corner of the village" (BTW, if you don't know your directions without a compass, learn them [or carry a compass]). ALWAYS IDENTIFY WHO YOU ARE AT THE BEGINNING AND END OF A CONVERSATION. Nothing is worse then not knowing who you are talking to.
Also, read the following link. It's geared more towards HAM radio, but there are many good lessons that can be applied to airsoft radio use as well:
http://nacs.uci.edu/network/Radio_Operator.pdf