When I skirmish battle in Command and Conquer 3: Tiberium Wars Turtle Tactics is the way to go. Now if your asking yourself what is Turtle Tactics? I can explain a bit about what I mean.
Turtle Tactics refers to a style of gameplay where you build up your base with heavy defense as well as preparing a heavy offense. You wait till your base is well defended until you strike at your opponent. First I like to start off with building a Crane right off the bat. This gives me the ability to double my production thus giving me an upper hand against someone that likes to rush an opponent during a skirmish battle.
From there I will build a Warfactory, so that I can produce multiple Rig Units. Rig Units allow me to protect my base quickly and effectively with the provided double cannons on top of a stealth detector and repair drones. The enemy will usually attack these battle bases without attacking any nearby Tanks or Pitbulls allowing those units to flank your enemy quickly and effectively.
After I have built a Tech Center I build two Sonic Emitters and place them side by side making the emitter twice as powers eliminating enemies with one hit instead of multiple hits. With this combination I am able to effectively protect my base without any enemy interference, and build an army strong enough to strike once and end the war.