Time to dig

All right, you've done your recons. You know where your MSR (Main Supply Routes) into your area are, you know where the choke points are and you know the best spots to ambush them. Time to go home and wait for the shit to start, right?
Wrong. Go dig some fucking holes. Scout out those areas some more and figure out exactly where the best spot is to place your effective fire, then dig your emplacements, whether they be shallow depressions, classic chest deep foxholes, shell scrapes or even small bunkers. Of course, use the utmost discretion while doing so.
You need firing positions and cover. Take lessons from the Viet Cong who prepared their ambush sites weeks, months and even years in advance. It's a hell of a lot easier to do your combat preps before the shit gets out of hand than after. There ain't any drones flying overhead now, right?
If you prepare these positions now it'll hardly be noticeable - you'll just be digging holes if someone were to see you doing it. But if you wait until hostilities begin, your digging will be recognized for what it is. An added advantage of doing it now is that in a few weeks they will be well camouflaged with natural vegetation growing up and around it. You also want to clear firing lanes and nothing screams Tactical Position like freshly cut firing lanes. If they're prepared in advance, you won't have all those white cuts on shrubs and trees pointing right to your positions - they'll age and brown and look completely natural.
Small bunkers especially. If you construct a bunker and then place your dirt on top of your overhead, then pretty soon you'll have weeds and grasses growing out of it and it'll look just like a small hump in the field next to that major intersection.
Cache some ammo, water and MREs nearby so you don't have to pack that shit in.
Plan your site well and most importantly, plan several escape routes. A Patriot that gets away lives to fight another day, but a dead Patriot is, well, a dead Patriot.