It's gotta be easier than I think it is...right?

So, I was talking to my jewelry teacher who has been selling her jewelry for years, and i was asking her questions about selling. I know that a lot of it is trial and error, but I want to know what I always need to do, no matter what is going on.  Trial and error is cute and all (i hate not knowing what i'm doing, can't you tell?...."control freak" is a little harsh...I prefer "avoider of drama"), but I want to make sure i'm not neglecting something i should be doing while learning as i go.

So far, the things that I know are:
-keep track of receipts/expenses
-keep track of inventory and costs of items
-keep track of what i sell and how (how much is on consignment/how much is on taxes/how much is under the table where you should report it unless you want to go down like Al Capone -and almost as Albert Anastasia....I LOVE mobster biographies on the bio channel :)  )!!
-I also learned details about how the state has you pay the 6% sales tax (in connecticut they do it quaterly during the year, at least when you first start off).

*I'm thinking about going for Dava (a local store that everyone in the new haven area knows about..it has been around for 30 years) as my first store. What's the worse they will say...no?