You can have knowledge of designing and experience as well. However, it will still be difficult to fit in all the elements of graphic designing in a particular layout. Hence, it is always a good idea to go by the rules.
All the elements in your design need to be balanced as that will give a smooth flow to your design. Major elements need to be on the centre position whilst margins need to be on the sides. You can add reflection and rotational symmetry for interest.
Always make a three by three grid while working. The key elements need to be at the focal point where two axes meet. It is popularly known as the rule of third.
The graphic design layout principles focuses on the rule of unity. It states that all the elements must be uniform. They should be aligned to the grid with a uniform size. The dimension needs to be equal as well.