New players of Civilian Defense don't often have an appreciation of how the new game mechanics translate into new strategic focus. Specifically, in a typical 1v1 in vanilla FAF, you only have to focus on one thing: The enemy. He has an army, ACU, and a base. Maneuver of the ACU/Army and macro of the base, against the enemy's ACU/Army/Base occurs.
Civ Def changes this significantly. First, the introduction of attack beacons gives the attacker an initial, powerful advantage: Attacking players will have numerical superiority early in the game. Attackers should therefore focus on strategies that allow take advantage of this by raiding heavily and attacking enemy forces. Earlier is better. On small maps, you can raid as soon as you have your first tank spawn. On larger maps, you should go air-first and build a transport. This will allow you to drop your spawned units at key areas around the map.
Second, defenders will be out-matched by equal skill attacking players until they can generate a significant bonus from evacuating civilians. Therefore, defenders should primarily focus on defending themselves and the civilians. Moving ACUs to civilian camps will greatly help in fending off raids, as will building defensive structures there. Expansion, as compared to a typical 1v1, is less important because the bonus given from evacuatin civilians will provide a greater long-term benefit than a few addition mex: Evacuating only 20 trucks will provide +100% resource generation. Also, because of the "must survive" number, if a defender allows an attacker to kill too many civilians, they can lose.