More turrets, laid out in a sort of funnel-fashion, like a roach motel. You want them to come all the way in and get themselves surrounded, before they grind to a halt. But make sure you don't block off your exit, in the process.
Personally, I like to make sure that I've got at least 6 ITBAs mining different patches of argentum, if I can help it. I'm also a big fan of multiple barracks and factories.
Also, stick to heavy marines and walkers as your favorite troops on this level. Basic marines seem fairly worthless, an as I understand it, Tanks are mostly there as linebackers, to soak damage.
Oh, and you might make a point of saving at points, using all the slots, when you feel that you're doing good, so that you don't get frustrated having to rebuild your base a dozen times just to get back to that point where you should have done something different.