I'm also a newbie, but here's what I've found through research:
1) I save the best quality for my prints. I uploaded smaller versions to my page, so that people can see what they look like BUT they can't snag it and make a huge print with it. As far as watermarks go, I've seen arguments for either/or, but I think the general consensus is that a smaller preview picture is a better means to prevent theft.
2) I plan on making to order, and adjusted my processing time accordingly. There are pros/cons to making to order, or printing and selling. When you make to order, you don't have dozens of potential prints collecting dust around your house, but it does eat up profit getting the prints shipped to you. If you print and sell, you can order in bulk (save on shipping) and get them out quickly, but you risk having prints that don't sell.
3) I researched prices for prints of my size and style. I also took into account how expensive it is to print each picture. And when you open up, you don't want to price it too low in an attempt to start off with some sales; it could have an adverse effect where people don't think your stuff is good enough.
