A tried and true method. Cut scrap paper to the size of the frame and mark the nail location on the paper. Using painter's tape, move the paper templates around the wall until satisfied. Then hammer the nail through the marks. Remove the paper template and hang!
My hubby and i started doing this with one dollar bills when we got married-- after about a year, i [just me] had several hundred dollars and got to enjoy a great birthday vacation and still have lots left over :) Great Idea To Save Money
Keeping a Clean House When You Have Young Kids at Home