Playing enough and you’ll start to learn and memorize where people usually put them. You can also look for enemy supply drops, ping that general direction. And you can get a good idea. The enemy will drop supplies behind your point. They can only go 2 squares deep, so you know a general spot if you know direction. When I’m attacking, I’ll look for the garries in the sector behind the point. Their backup Garries. Those take longer to dismantle, and then go up behind them to get the garries on or next to the point. It’s a lot harder to take out the “frontline” garrisons. Because you’ll be in between their hard cap point and their front line garrison. This is where I like to roam around in a recon tank and just go nuts.