I use two methods simultaneously. The first is to name for function, examples are Field Label, Column Header, Portal Header. The other is to describe styles, examples are Default, Default Small, Default Black. I use abbreviations in combination with those, a few examples given below.
One thing that I have found useful is to have several themes. A theme for user interface layouts and another for printing is the minimum. I prefer to have more themes that are more tightly focussed that have one massive theme.
One thing I don’t do is include font names. A theme has one font-family.
LA ( left align - default )
CA ( center align)
RA ( right align )
VT ( vertical top - default )
VB ( vertical bottom )
VC ( vertical centre )