If you want to be a bad product manager, just start being a product manager. If you want to be a good product manager, you need to work at it.

If you want to be a bad product manager, keep changing your mind about the strategy and direction for your product. If you want to be a good product manager, set the vision and direction for the product and make changes only as needed.

If you want to be a bad product manager, assume that domain knowledge is all you need to succeed. If you want to be a good product manager, make sure to have the right amount of knowledge about the domain in which you are working.

If you want to be a bad product manager, listen only to your customer needs when defining your product. If you want to be a good product manager, make customer needs the central but not the sole voice in product definition.