Go to lots and lots of other music stores. Figure out what you like and don't like about them. Go to other types of retail stores as well. Look at the layout, the floorplan, what works? Be prepared to work really hard and make no money for a couple of years.

Don't spend a bunch of money on advertising. Most of it doesn't work. Get free advertising - word of mouth, flyers in other businesses, giving products/gift certificates to local auctions & other fundraisers, etc. Throw a grand opening party and invite all your friends and ask them to bring other friends along. It doesn't matter if they are musicians, they know and will meet musicians. When you do spend money on advertising, spend it somewhere that you would want to give money to anyway: advertise in the high school play program, be a sponsor for a community concert or festival.

Okay, when it all comes down to it, customer service is key. You can sell the most beautiful instruments on the planet, but if they are tainted with poor customer service, forget it. You might sell the instrument but the customer won't be back. People who are buying an instrument for the first time can find it very intimidating to walk into this kind of shop. Be nice, be informative, be helpful, be honest. Even if they don't buy from you they will tell everyone they know what a great store you have. If you dish them a bunch of attitude and make them feel stupid, they will tell everyone they know about that AND they'll tell a bunch of people they don't know, too, in forums like this one.

Owning your own business can be the greatest thing in the world if you really believe in what you are doing. Have fun!

All the best,
Sunga