First off, don’t open and close the oven when you check on the cheesecake! It disrupts the baking and introduces new dry air to the humid oven. That being said, you can start checking the cheesecake at the end of its bake time. You want to pull it out when the edges are firm and the center still has a slight jiggle to it. It’s hard to see if the cheesecake is done because it doesn’t brown, but you can check the center with a toothpick to help you know for sure.