General guidelines, find a good wholesaler, and do your research. Don't just sell products, provide a service, such as readings, and such to give to your customers. Help them with research, educate them if necessary. Hold workshops and classes as well.
To help make your adjustment into the community acceptable, to avoid the problems we had (broken windows, broken down door, etc.), aggrege to educate and hold workshops on the various pagan religious types to the general community. Hold free sessions, etc. to offer people.
Best to spend on good quality store furniture. Best to buy quality items and sell at a decent price.
Get listed on WitchVox.com Great place.
Advertise, and join the BBB in your area. Also consider joining your local Chamber of Commerce.
I recommend setting up your hours for what is available and done within your community. So if most stores are closed on Monday, close yours on Monday as well, so that you don't provide a commerce shock to the area.
Keep in mind that you are not going to be considered a niche shop, indeed not. You are a community shop, that is a shop that is available throughout the year. One that doesn't close or dwindle after the tourist season.
Keep in mind also, that you need to provide an open and safe environment for your patrons. There should be no tolerance for harassment, ect of your patrons out in front of your shop, or in your shop.
I recommend carrying some form of New Age book shop/section for your store. The reason for this is that people like to read, they like to learn. And the more they read, and the more they come in to buy/return books, the more face you receive per day.
We started a library program for our store, and did wonderfully!
Check out places such as azuregreen.com and look at their wholesale program, they are great.
Check out stores and suppliers in Canada, as well, as they provide great products for cheap.
Consider hosting local merchants, etc., within your shop.
Main steps: Get your state business license from your secretary of state. Get your city license if needed.
Find a good location, open your store. Get some form of security. Make sure you don't need a security permit from your local police department to operate a security system.
Get some form of security camera system in y our store, this helps cut down on losses due to theft. Trust me it will happen.
Find an open minded land lord. Don't go with one who is 'unsure' but go with one who likes the idea of a pagan store in the area.
DO NOT CALL YOURSELF A WITCHCRAFT STORE. Absolutely not, you are a Pagan Resource Center, or a Pagan Store. The reason for this is that 'witchcraft' no matter what spin you put on it, will have a negative connotation to those around you in your community. However if you are a Pagan store, or Pagan Resource Center, you have much more credibility.
Join local stores in initiatives, and such to get your name out there. Help with local planning of events for your community.
Lastly, advertise as best you can.