The most important part to finding a good product is first finding a good supplier. If you already have your business license, resellers permit, and your seller central account set up, then you're officially ready to start getting in touch with suppliers.
Start with going through the Sourcing Introduction lessons and then move on to the Finding Suppliers lessons. Those will teach you the ins and outs of getting set up with the right supplier. You can also focus on the Vetting Suppliers and Working with Suppliers lessons as well.
Once you've got a few good suppliers lined up, then you can focus on the Product Research lessons which will help teach you how to identify good products that you receive from your suppliers. This will help you to know which products look risky and which ones seem good to jump on.
The process is to 1. Find Suppliers, 2. Vet Suppliers, 3. Open Accounts with Suppliers & Get Pricing, 4. Analyze Products, and 5. Make a Purchase.