Herald

A herald can come from any background or prior profession. Though most are from a learned class of people that can read and write. Often they are former monks who wanted to do something more than illuminating manuscripts of the various deities or deity they happen to follow.  They also require a very good memory in order to remember which heraldic device belongs to this lord or that lady.
A herald generally has some capacity to fight. The world is a dangerous place, and while protected and considered neutral parties, there are some that will do harm to a herald. Bandits, creatures, those who feel that they are above the conventions and morals of the lands.
A herald should also have a silver tongue. Speaking in a manner that brings calm and content to any situation. Being able to see the middle ground and suggest it to opposing parties. These are skills a herald should have. But not always, some heralds will just smash their point of view to the forefront. Diplomacy is a virtue. 
Having an artistic flair and touch of creativity is helpful when working with a new noble or knight. It helps in order not to have everyone's heraldic devices looking similar with the only difference being a line or extra icon.
The heraldic device must be created out of a limited variety of colors and patterns called tinctures. These represent metals, furs, honorable and dishonorable colors. The background color can be divided into patterns rather than being a single flat color. Further division of the device is accomplished with ordinaries, these being easily recognized devices such as crosses, pales, bends of which any might be dishonored by making it a sinister. A sinister mark made in the opposite direction. 
Devices also have charges which can be any plant or animal and all their variations. More often than not being something thought of as beautiful or powerful. Though the ugly and horrific have been used as well. Those doing so generally are not though well of.
Finally there is marshalling which denotes to whom the bearer owes allegiance to. Or inheritances added to an existing device.
It takes a good memory and personable personality to be a herald.