What is the best method to geometrically show the addition of complex numbers?

Multiplying a complex number by a real number

Explanation:

For example, 2 times 3 + i is just 6 + 2i. Geometrically, when you double a complex number, just double the distance from the origin, 0. Similarly, when you multiply a complex number z by 1/2, the result will be half way between 0 and z.