Well, if you can easily manage to move your sub around, then just split the room into a number of "zones" (however many that you feel like moving the sub to), and just see how things sound in each zone. No really easy way to tell you where it's going to sound best, and generally the corner will make it "boomy", for reasons that iwearnosox suggested. I'd move mine around if it wasn't so fvcking huge. 🙂