I recently opened an online stamping and scrapbooking store. I knew absolutely nothing about running a retail online store, but have learned SO MUCH about pretty much every aspect!
First decide what type of business (sole prop, llc, corp, etc). Definately discuss this with legal council! Apply for a Fed Tax ID, if necessary.
Write a business plan (include what you want to sell and what your goals are); you can get info on this online (this one is helpful:
http://www.hcmpublishing.com/Small-B...ness-Plan.html).
The next thing you have to do is think of a name and register with your state. You also need to get a resellers license (state) and set up a sales tax account (if applicable in your state). Then you should open a business checking account. Business credit card is helpful, too.
Now you can plan exactly what you want to sell (writing a business plan can help with this, too) and start requesting information from manufacturers/distributors.
Other things to keep in mind: shipping, product storage/organization, advertising, competition, audience, profit margins, accounting, site design, web hosting, start-up costs.
Your state government probably has lots of good information on most of this. I wouldn't mind chatting, if you'd like...
Cheryl Kay