Depending upon what I see when I check outside I will open the about a foot with my hand on the back of the door and my leg behind the door to help keep it from being shoved open. I do not open the storm door until after I determine if there is a threat. If a BG he has to open the door which is locked which gives me time to swing my chosed firearm in front of me. If determine it is safe to go outside I will. I have a couple of dogs that get excited which usually detour strangers from wanting to come inside and since they look "uncontrolled" I have a great excuse to not be bothered by fluff.
Many times I can peek out the window to see who it is, grab a gun, and then exit via the garage to see what they want outside. With the dogs they aren't interested in coming in. I'm armed and ready which reduces the risk to me.
My house is pretty well set up to see who's there and prevent a forcible entry. With a gun its much easier keep the threat outside. I don't have a problem letting a stranger that I may perceive as a threat see a glimpse that I am armed.