The leader of the celebration was called Janis -- a common Latvian name; one of the requirements of being a leader was to be called Janis (Janu tevs). He handed out beer and wore an oak wreath while his wife (Janu mate) handed out cheese and wore a flower crown.
Then, the people lit bonfires and sang songs while dancing. The songs included the word Ligo, which mystically brought the god Janis to the land to bless the fields and give them an abundant harvest. He was thought of as tall and handsome, riding a horse and wearing an oak wreath.
Children traditionally went into the woods on Jani, searching for the fern blossom (like a "snipe hunt" in North America, since the fern blossom does not exist) which supposedly bloomed only at night on Jani. Searching for, and theoretically finding, the fern blossom brought good luck. Adults jumped across fires and danced ritual dances around the fire or a sacred oak.