The only ways I have seen for this are
1. Wear heels with all your costumes. If it's a costume with boots (like organization XIII) MOST people wear heeled boots.
2. The other person squats a little. This I have seen a few times.
Other then that I don't really know..
Cosplay DA Regular DA
-Fate Testarossa (Mahou Shojo Lyrical Nanoha A's) ~90%-
-Ryouko Ookami (Ookami san and her 7 companions) ~75%
-Amy Sorel (Soul Calibur) 25%-