First go to the news page to see which products are new to Neopia.
These are usually great for HUGE profits.
The key to getting these items is to do a couple of things
1. Know restock ti'mes (Which is a pain because they constantly change)
2. Have a program that alarms you to these ti'mes (I.e. Alarm ++ for Windows)
3. Turn off load pictures on your browser (this wastes precious seconds you'll need to grab the new stuff)
4. Only use Ctrl-R to refresh the page
5. Use the tab button to put the cursor in the wagering box once the "Haggling for.." window opens (Internet Explorer is better for this, it allows you to overwrite the zero first found in the wagering box)
6. If you do manage to get great new stuff, undersell the competition by about 15%.
It may seem like you are losing a lot of money, but you make your profit by selling in quantity while their stock rots on the shelves.
Enjoy