There are specific techniques to follow when learning how to shrink clothes properly...
Use the hottest water setting available on your washing machine. High heat causes certain fibers to tighten and shrink up. The spin cycle will help to further shrink and bind clothing fibers tightly together. Once the spin cycle has been completed, put your clothes into the dryer. Set the controls to the hottest settings again for maximum shrinkage. Then remove the clothes from the dryer and iron them. You should notice they are not as large.