Graphic design is more than what meets the eye
The purpose of designing is to communicate an idea. If the message is confusing, then that’s not a good design.

The design must convey the benefits of the product
Whether you’re selling or not, your potential customer must know what’s in for them. Remember people is going to invest money in your product.

The design is not for designers
Remember that the focus you need to give the design is for the customer’s needs, and not the last piece of your portfolio.

The design is not an ocean, it’s a fish tank
Remember that marketing and design ideas cannot be exchanged. If the design worked for you, it’s not necessarily going to work for somebody else.

Designing is creating something believable
A good design will attract more people than standard designs.

Source: Idea Book