I wrote about the Day of Three Kings a few years ago, although my post wasn’t really about the Three Kings tradition per se. I witnessed the custom performed in a Moravian village this year. Three children about five to seven years old (all of them happened to be girls) came by, rang the doorbell, lined up and sang the Three Kings carol to us. They were dressed as Kašpar, Melichar and Baltazar, each initial printed on a paper crown on their heads. They gave us a packet of sugar and frankinsense. The girls were accompanied by a woman who carried a donation box. We made a donation and she proceeded to write the inscription K + M + B + 2011 on the doorframe with a chalk. The inscription supposedly means Christus mansionem benedicat (“May Christ bless this house”). The donations go to the Czech Republic Charity (Charita České republiky).
Here is a link to the Three Kings carol: