Hi K C,
FWIW, I use large, medium, small, and xsmall fonts for my
headings, which are in Verdana online and Arial in print. Normal
text is also in Verdana online but in Times in print. (I was
brought up hearing that big blocks of text are faster to read in
print when in a serif font and faster to read online when in sans
serif.)
To distinguish the different heading levels, I change the
indent (my Normal style is indented in 20 px from h1 and h2 but
shares the same indent with h3 and h4). I also use color and bold
for the headings, which really sets them off and allows my h4 to
use the same xsmall font as Normal.