If you’re unfamiliar with the area in which you must back up, you should:
Get out of your vehicle and walk around the area to become more familiar with it.
Not use both side mirrors because it can be distracting.
Wait for someone else to back up in the area so you can see how they do it.
Before backing up, you should get out of your vehicle and look at your line of travel. Check your clearance to the sides and overhead.