Try this one...

Take all of your irons out of the bag and line them up in front of you. Pick up your longest Iron ( for me it is a 4 iron) and hit a shot with it, if it is a good clean shot, then move to the 5 iron, then to the 6 etc etc. If at anytime you hit a shot that you are not 100% happy with, go straight back to the longest Iron and start again.

The reason I do this is because it really keeps my mind focused on preparing for a shot as I dont want to start all over again !!

If you get round the clubs once, then try to get round again. It beats just hammering balls up the range.