I highly recommend that you wear nude underwear and, if possible, strapless or backless bra (it depends on the style of gowns you want to try on).
I ask you to wear very natural make-up to keep the gowns in a perfect state.
Also, when determining the length of your gown, it is crucial that you have a clear idea of the shoes you plan to wear on your wedding day. Should you have them already, great! Bring them with you!