An important part in preparing for Jāņi, which is the mid-summer festival/most important holiday in Latvia, is the making of the wreaths. Both men and women wear distinctive wreaths on their heads for the holiday. Men typically wear oak leaves on their head like this gentleman is wearing.
Women have a lot more choices as they generally choose flowers as the main part of the wreaths. Daisies are Latvia's national flower and so they are oftentimes the center piece of the wreath.
A few days before Jāņi down near the Freedom Monument in Riga there was a public wreath making event where you could come and get the flowers needed to make a wreath and you could get some lessons if you were new to it.
Folk costumes weren't required but you might stick out like a sour thumb if you weren't dressed in one.
Another Jāņi tradition is that on the night itself you would jump over the large bonfires that are burned which would ensure that you would have good luck in the coming year. Here a short clip I filmed of one of the bonfires at the Riga Jāņi celebration that wouldn't be able to be jumped over for many, many hours yet.