Every Neopets user is allowed to open up their own shop for a meager 150 NP investment. This is well worth the price, since items you'll find during your travels around Neopia will fetch hundreds and thousands of Neopoints in the long run.
The first things to do are- name your shop, choose its location (either Neopia Central, Mystery Island, or the Haunted Woods), add a little description, choose a shopkeeper, name your shopkeeper, and add a friendly greeting. Then, for an ever-increasing amount of Neopoints, you can increase the size of your shop so that more items fit inside. For every one level of upgrading, your shop can fit five more items.
Once your shop has been set up, you may notice that you greeting is not what you set it to be. This is a weird glitch for the first time you enter a greeting, but from this point on you can make the greeting almost anything you want, although there is a special filter that doesn't allow certain words to be used.
Now you can go to your inventory and fill up your shop with all the items you want to sell! Then you can return to your shop by clicking on the little yellow building (second in from the left) in the menu at the top of the page.
This page allows you to set whatever price you want (from 1-99,999 NP) for the items you're selling. Anything with a price of 0 NP does not appear in your shop, and anything priced from 100,000-250,000 NP can be seen but not purchased. You cannot price an item higher than 250,000 NP.
Once somebody buys something from your shop, the Neopoints you've earned go directly into your Shop Till. You can also see who bought what and when by going to the Sales History page. To see what your shop looks like to other users, select Shop Front.
Some users like to add blogs to their shops. These are nifty little pictures with scroll bars on the side that add a theme to your shop. Check them out and see if there are any you like.