Play as the GDI. If your enemy likes air units or missiles, surround your 
base with the Firestorm Wall at a distance from your base, backed up with 
RPG Launchers. Whenever aircraft or missiles are detected coming toward you, 
turn the Firestorm on. When aircraft attack, wait until just before they 
cross the Firestorm line so that they cannot turn away before they are hit.
Do not worry if the Firestorm is attacked by the enemy aircraft -- it is 
pretty tough. Just bring some MRLS in to assist destroying the aircraft.