I just setup all of the official stuff for my shop recently. I went over it with my tax guy and it seems good. This is what I've done, but if you have an accountant/lawyer you should consult them about your specific business.
I got an EIN (it is free) and I filed as a sole proprietorship as I'm working solo. It was explained to me that I shouldn't form an LLC until I have 10k (for tax purposes) in net revenue a year or if I'm in a business with a lot of liability where you're likely to get sued (say food, people can claim they got sick etc). I have a very low liability risk, so that's why I picked what I did.
I also got my DBA (doing business as) since I'm not doing my business under my own name as I named my shop "La Reveuse Design", I think this was only $15 unless you want to rush it.
I got my TPT and since most of my sales are national rather than within AZ, I set it up to pay them annually. I asked my tax guy specifically about this because I was making sure I handled it right since I really don't do much business within AZ and I wouldn't collect sales tax on orders from other states.
Then I was concerned about quarterly taxes because it's something I've never done. If you owed money on your tax return the previous year, this is something you might have to do. It's not something I have to do yet as I don't make enough and my husband and I received a refund the precious year.
Also with a business and being self employed, you'll have to file a section C with your tax return, so if you're not super savvy with taxes, I'd hire someone. If you have an LLC or something, you'll have a separate return for that.
Anyhow that's what I did. I also just realized this post is pretty old so probably not helpful but I guess in case anyone comes by