I found deciding on "must have" features helps a lot. For example what color, style etc. you want. train or no train, strapless or with straps/sleeves/etc. For me must haves where: 1. bright color, preferably orange or yellow or red: 2. not sleeveless 3. light chiffon. Then I fell in love with Roberto Cavalli's collection, from I think spring-summer this year, and so I wanted the dress with either his pink floral pattern or blue feather pattern. After that it was a matter of time to find the right dress from that collection and for a right price. I did try on random dresses during "in between" period, but it was mostly to see if there was a substitute. But as I said: first decide on the "must have" features, then perhaps on fabric, color and so on.