I wear a headsweats skullcap - very light wicking mesh that protects top of ears and back of neck along with areas exposed by helmet vents. It is a light color and is comfortable.
Keeping the sun off the skin helps if the fabric is very light and wicking. There are long-sleeved jerseys and sun sleeves for that purpose. I can't vouch for them, but some of my friends do so even on hottest days.
I normally wear sunscreen only if I will be out for several hours 10am-4pm. Usually I avoid this timeframe as it's too dang hot. I use a spray, either Neutrogena or one of the other high SPF ultra sweatproof types.
Otherwise I take no extra precautions. My skin tans easily without burning.