as Pix said; you start with the default; usually the defauls usually means “makes sense” at least in the time they were first set.
then you make usually traces; network, bsc or cell level.. wehre you can see whats the average rxlev or txlev for both site and mobile… and you change your PC parameter accordingly.
you can ask your vendor… since some vendors have some extra parameters that help optimize PC.
regards