I have gone to the trouble of writing up a list of radio commands in order to inform you of what they actually are, but the way you use them is just as important. Everyone can give and receive these commands, but you must use them in moderation and when they are required, or else people will just ignore them (think of the boy who cried wolf). If you need repairs, then send the message once. If no-one responds within 10 - 15 seconds, then try again. If you hold down the button and fill the message box up then everyone will most likely ignore you, or get annoyed and leave you alone, punishing you in effect. Radio commands are very useful if you can memorize the important ones; they save you writing out the particular message in full, and they give some audio to make it noticeable, especially if your team has their speakers turned up, although they are non-customisable and generic. So if you do have the time, a "gimme some help quick at spawn!!" is more effective, especially with less receptive team-mates, although often a radio command will suffice. Sometimes you need the extra information, because you could be looking for a needle in a haystack if the message was just "I need repairs" but "I need repairs on the hill" is much more informative and gets you the help you need quicker.
BATTLEFIELD ORDERS
ALT+
1 - I need repairs
2 - Take the point
3 - Move out
4 - Follow me
5 - Hold position
6 - Cover me
7 - Take cover
8 - Fall back
9 - Return to base
0 - Destroy it now
RESPONSIVE/INFORMATIVE
CTRL+
1 - Building needs repairs
2 - Get in the vehicle
3 - Get out of the vehicle
4 - Destroy that vehicle
5 - Watch where you're pointing that
6 - Don't get in my way
7 - Affirmative
8 - Negative
9 - I'm in position
0 - Enemy spotted
INSTRUCTIONS
CONTROL+ALT+
1 - Attack the base defenses
2 - Attack the harvester
3 - Attack that structure
4 - Attack the refinery
5 - Attack the power plant
6 - Defend the base
7 - Defend the harvester
8 - Defend that structure
9 - Defend the refinery
0 - Defend the power plant