How does one become a Wizard Saint? Being a Wizard Saint means that you not only hold great power, but are also highly respected and well known, like Makarov. Also you get a cool looking badge too as seen below:



But what factors does the chairman of the magic council take into account when deciding whether one is "worthy" to become part of the Ten Wizard Saints?
As far as we know it's not (or not necessarily) the chairman of the Magic Council who decides who becomes a Wizard Saint. In Erza's vision about her funeral it was stated that the vote of the entire council decided that she should be a Wizard Saint. Later Jura also states that it is the Council who appoints the members.

With that in mind, I'm pretty sure that the Council takes whatever factors they want to take into consideration when pointing out Wizard Saints. Which means there is not a single score sheet, and if you score 5 points in magical power and 4 points in teamwork then you can become a Wizard Saint.

Strength however is one factor that they definitely consider, but that' not an ultimate factor for the decision as Jellal, for example, being a Wizard Saint was defeated by Natsu and that didn't make Natsu a Wizard Saint.