Well from my experience the chest spawn random, the only sure things I have come across are following the outer path along the edge of the ground when you spawn in to your left. Also chests tend to spawn in on sides of building a lot. Most chests reset often and once you have made your rounds through the environment I have found if you turn back around and make your way back to the start a good amount of them have returned. Also very good places to find them are on cliffs. I am a lover of exploration and I spend hours just searching, reminds me so much of Borderlands 2. ^_^