As I begin to write this i realized that a lot of this is similar to venue shopping:
1st - Envision your day. Is it inside? Outside? What season? What colors? What dresses fit this location?
2nd - Dive in and explore this amazing vast space we call the world wide web. There is so much to see and help and overwhelm you.
3rd - Do ask questions! You can learn a lot from the pros. They can help understand your vision and whether the dress fits best with the venue. They can help with cost saving ideas and alternatives to the traditional wedding dress.
4th - Talk $$$! The same dress worn once may be online for you to buy. The salon may knock off money as long as you use their tailor or buy bridesmaid dresses there.
5th - Shop around! Get as much information as possible before you visit. Go in with pictures to help the salon choose dresses that you think you'll like.
6th - Visit multiple shops to see what styles and prices are out there. Take pictures (if you can) so that after the overwhelming day is over you can organize your thoughts. I brought a friend that discretely wrote down information as i purposefully asked the consultant detailed questions about the dress. This really helped later when going through the dresses i tried on.