Know your budget and stick to it. "The worst thing a bride can do is try on a dress that's way out of her budget,and then fall in love with it". After that, it'll be hard to find a dress you love just as much in your budget. One way to safeguard your experience is to be honest about your price range.
Set aside a special day just for dress shopping. Go glam, have your hair done and your makeup so that you feel your absolute prettiest the day you try on gowns. You want to be fresh and relaxed and enjoy every second. Underwear is important but I will do my best to help you with the right underwear.
Pin it! start a wedding dress board or start a scrap book with pictures of your favourite dresses. It's great to have a few pictures of dresses you like, but keep your options open. It is good to try on dresses to check how the style suits you rather than the girl in the photo. You can try on a variety of styles and fabrics so you can see how they look on you.