Something I try to do on defense is pull of a surprise or two. It doesn't have to be anything big but just something that will throw your opponents attack off a little.
Another thing is TRPs. TRPs are great on defense, especially if you are playing as the Russians. I will usually place a TRP up near where I set up my first line of defense. As they start to get over run I call in artillery on that position right after I've pulled out and the enemy moves in. Also if I'm not covering every flag on the map I'll set a TRP on a flag I'm not going to defend and as the enemy moves in to that flag I'll send some arty their way.
Hey dieseltaylor weren't you going to send me a setup?