general idea behind materia magic: construct a symbol of your intention, energize/consecrate/empower symbol, place symbol as near as you can to the place you want its effects felt.
other workings tend to focus less on a physical vessel for the spell, but still emphasizes the use of symbols in its castings. in these workings, the caster arranges symbols of the desired outcome in/around/on the recipient and empowers those symbols with spiritual energy. the variables of the ritual itself are what symbols to use (images, sigils, natural materials, colors, timing, herbs, stones, shapes, etc) how those symbols are constructed and placed around the target, and then how the whole display is energized to do its work.
when the target cannot be reached directly, a proxy can be used in its place. this proxy is just another kind of symbol at its most basic. an item that is covered with symbols to indicate the identity of the person/place/thing its ment to represent.