Have to second Pillar, spread out. Keep your squads in command though, or you're asking for routs. And accept the fact that sometimes you're just SOL concerning artillery and that you're going to have to grin and bear it. Also, mortars in particular are vulnerable to arty, I've noticed, try to keep them away from it because they get knocked out REAL easy.
I've noticed human opponents will tend to drop arty early so you might be able to take advantage of that.