On the first Friday in December,from 6 to 8 p.m., shopkeepers move all the merchandise out of their front windows and stage live holiday performances for onlookers. As the rest of us begin our holiday shopping, they’re concentrating on sewing costumes, building sets, writing scripts and baking cookies for customers. Merchants go to great lengths to outdo one another–making each year’s displays even more impressive than before. The night itself is a celebration of the holidays. The District features open houses, strolling carolers, holiday treats,and visits with Santa.