Hi Paul
Do you have a printer at home ? Does it have a facility for the rule of 3 grid to be displayed ?
The reason I ask, we have a Canon iP printer and when you go into the printer software (not the print screen, but actually the Canon EasyPrint software) and get to the final print screen, there is an edit function, that allows you to show the rule of 3 grid lines, so you can adjust your photo if required.
But I found this a great tool, when I was trying to explain (not very well I must add) the rule to my daughter when she started in photography and it's a lot easier to visually see something and the difference it can make.
Hope this is of some help...