Solo I use the little room by the work bench for the Trample Steam, you can run a circle, or if zombies come from the right or the other building, half a circle, even zig zag if you want to.
Speaking of Trample Steam, if your playing 4 players, camp at the bottom of the ramp where the work bench is for the navcard reader, there's 1 window next to it. Place a Trample Steam there, then all 4 players stand around the area, the zombies can only come from in front of you making it quite an easy killing zone.
P.S. I haven't seen anyone mention it yet, but those teleporting crawler things, if you fire a shot you don't get a perk and bonus points, HOWEVER, if you all build Trample Steams.... they will get launched, killing them straight away and it gets you the perk still! (from what I've seen, they also don't attack the Trample Steams either, I'm gonna test this further, but they seem to focus on the players and not get distracted by the Tramples and attack it, unlike the zombies.)
Hope this helps out too