May and June are the season -- for senior prom, graduation and open houses. Parents, if you have a graduating senior or a student going to prom, be prepared: it's expensive. Here are ways to trim spending on prom dresses, tux, graduation supplies and open house. Lady Greenwise (that's me) has graduated three seniors and picked up some penny pinching tips along the way. How to Trim Spending on Senior Prom and Graduation