1st thing to do is make sure your mirrors are spotless. 2nd thing is to set your mirrors correctly.
If you have reversing bleepers, TURN THEM ON. They get peoples attention, and the more people alert to your manoeuvre, the more chance of someone giving you a shout if you have missed an obstacle.
And as others have said, if you are not sure get out and have a quick nosy. It says far more about you as a driver IMO.