Tattoos
For most of Glorantha, literacy is a concept that isn't taught in schools. For one thing, schools don't exist. For another, many forms of literacy are cult secrets. However, that is not to say there is not a rich written/drawn language, it's just that it varies from place to place and person to person.
Many people, chief among them the Orlanthi, will have multiple tattoos, denoting their tribe, their clan, and the things important to them. These are not in themselves magical, but can be made the focus of magic. They may connect a person to their understanding of a rune, to the wyter of their tribe, or to the spirit magic that they hold. Tattoos track social status and important events in lives, and a set of tattoos can serve as an introduction and a set of references. A person can often be described by their markings much more easily than by their features.
Praxians and Grazelanders find tattoos less important, but still have tribal markings, possibly ritual scarification more than pigmentation. They are also more recogniseable by habits of hair cutting, sacred dress, or their choice of animal skins.
Focuses
For spirit magic to work easily, it is important to have a focus for the spell. In game terms, lacking a focus means having to focus without help, and delays any spirit magic by a round. In character terms, a spell or a connection to magic is an important thing that should be marked and respected. A focus may be an object, or a sacred shape or mark - these are often tattooed on, but could be painted or burned or scraped, if the skin is to be marked.
Game Effect
Most of the game will not require players to keep track of their focuses, fetishes, magical ephemera, and small belongings, but please note that if you wish to do so, the GM would be delighted to have any and all information about characters.