Practice your tip stance as basis for good body mechanics and easy power....

Turn the back knee to kick start the kinetic chain (sequential transfer of energy through body segments) as a basis for efficient generation of body speed leading to relaxed and easy power.  Can be practiced at any level of play from mini tennis to pros.  When practicing the tip stance ensure the back knee turns and heel lifts prior to contact, not on or after contact.  The timing of this is key.