Perry Hill is considered one of the top infield coaches in baseball. He is currently the infield coach for the Seattle Mariners and has previously coached with the Marlins, Pirates, Tigers, Expos, and Rangers. Perry's philosophy is to teach the "6 F's" - Feet, Field, Funnel, Footwork, Fire, and Follow. The 6 F's can be taught at virtually any level of play and break infield play down to basic core fundamentals. In this video Perry goes through each of the 6 F's in detail.
Perry also has an excellent website which provides a ton ofinstructional material to improve infield play. Check out Gold Glove Defense for more details.