Natural sunlight is (mostly) your friend on a real estate photo shoot, so make sure the blinds are open. How you open the blinds is probably more of a personal preference, but my normal course of action is to open all of the blinds so that the slats are nice and horizontal. If there’s too much sunlight coming through, it may be more beneficial to have the blinds tilted a little bit instead of horizontal, but this will be situational. It may also be beneficial to have them tilted a little bit if there’s something distracting outside the window. I typically do not roll up the blinds since that may let in a bit too much light and there’s always the risk of the blinds breaking (I’ve had that happen on more than one occasion).