1 It's not enough to have an idea. You need to make a mock-up and prototype to prove the idea works on a physical level.
2 Make a first-generation prototype using a competitor's product alongside the design or utility changes you intend to bring to market
3 When picking a product, start with the end in mind: who's the customer? Why are they going to click your Amazon listing? Which e-commerce distribution channel is this for?
4 Certain product ideas (e.g. fabric goods) are easier to iterate on than others (e.g. plastic or metal mold injections)
5 Pay attention to the ratio of "value to material". For example, plastic garbage bags are a commodity and sell for close to the cost of goods. But, if you melt them down into a surf board fin (which is a particular product niche), the margins increase.
6 some different material mediums you can play with: 3D printing, metals, plastics, fabrics, carbon fiber, electronics, glass, wood