Back stroke for swimming help???

What do you do after you finished one length of back stroke and you have reached the wall. I know how to do it for breast and freestyle but how do you do it if you're not facing the wall??? Also, how do you know when you reached the wall without hitting your head or hurting yourself??? It would be great if you can attach videos to your answers as well!!! I'm trying out for my school's swim team soon so the earlier you answer the better!!! Thanks in advance!