Welcome to Flowerchat!
I think a couple of the very most important things for new owners are things that aren't very obvious to new shop owners, at first.
Care and Handling of fresh flowers
There are some very specific things you need to do to help your cut flowers develop properly, and last in a consumer's home. You have to know when to toss a flower, and cut your loss, rather than send it out to a customer.
Floral preservative, Anti-transpirant, the different climates that some flowers need for storage, sanitizing of containers. There is much more, but these come to me right now. I would spend some time in the Product Care forums, and read all the information there, as well as find books on the subject, and ask your wholesaler for information. Hopefully your employee is well versed in this, and can help you as well.
Consistent pricing
Know your forumla for determning product retail values, and labor costs in arrangements. Make sure your $50 arr's or $100 arr's are consistent in the appearance of value. Coming from a position of someone who took over a store who had no clue of this, customers would tell me that they'd get super huge arr's for $50, or nothing at all. Some stopped coming because they didn't know which side the pendulum would swing on a certain day.
Nothing can kill a shop faster than flowers that don't last, and value that isn't consistent.
You've found a great resource here - good luck and welcome!
tracy