People celebrate by putting out multi-tiered displays of small dolls dressed in traditional clothing (hence the name "Doll's Festival"). (See pictures of dolls here. If that link doesn't work, try this one.)
Families with daughters still living at home usually have a small celebration at home, inviting friends and relatives for a traditional meal complete with amazake for the kids -- and, invariably, regular sake for the adults. Some families also make a visit to the local shrine to offer their wishes for good luck.
In Hawaii, which has a large population of Japanese-Americans, Girl's Day has become a universal holiday. In fact, in the days leading up to Girl's Day, TV and radio stations air ads targeting "men who are looking for that perfect Girl's Day present for their wife/girlfriend/daughter/mother/mother-in-law/secretary."
Oh, well. Any holiday that involves good food, good friends & family, and good times can only be good!
