I always use the side mirrors. I'll never forget when my Dad was teaching me how to back the trailers up. I think I was 12 and trying to back the trailer in at one of our local lakes here. I keep trying to use the rear view mirror and look out the back window. He keep telling me to use the side mirrors, and I was having a hard time with it. Finally he looks at me and says, Don't look out the back window, that's how girls do it. I still remember like it was yesterday, looking at him and have those words burn into my brain. Ever since then I've used the side mirrors. On a side note, now when I'm help someone back in that is new to it, I tell them that. Some think it's funny and some don't.