If you are looking to a physical product you must first look at your chosen market and make sure that you have positioned yourself in the right place within that market.
It is much better to be a big fish in a small pond than a small fish in a big pond.
Find a niche within your market then start to find your product and chose your way of selling it.
There are two major ways of getting your product to market.
You can buy wholesale or drop ship and there are advantages and disadvantages to both methods.
Wholesale means that you physically buy a product then ship it on via your sales medium to your customers.
The main advantage of this is that you can buy large quantities at a very good price, but this can also be a huge disadvantage as well.
The fact that you can buy a large quantity does mean that you get a great price, but you have either to get the warehouse that you have bought it from to hold onto the product and ship it for you or have a sufficiently large warehouse to store the products yourself.
Either way this will push your costs up and your profit down.
Unless you have huge funds with a massive warehouse it really is impractical to wholesale products.
Drop shipping is a great way to sell products if you get the right drop shipper.
You one that will sell you products in individual units and then ship in a reasonable amount of time.
You must get the drop shipper to send you a sample of the products you wish to sell and you must check that the product is of a quality that you would expect.
Do not be tempted by cheap inferior products, this will only bring you a whole heap of trouble.
If you can find a manufacturer of a product that you want to sell who will supply you with a picture library and does not mind you promoting their product online, then this is always worth a look.