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
-Stocking Anarchy (Panty & Stocking. Normal Ver.)
-Sora (Kingdom Hearts II Final Mix+. Limit Drive Ver.)
-Kyoko Sakura (Mahou Shoujo Madoka Magika)
-Akaito (Vocaloid. Black & Red Ver.)
-Marluxia (Kingdom Hearts Chain Of Memories)