Here's the rundown on how I did it. Know up front that you'll need flour, honey or sugar and baking soda, yeast, eggs, water, and salt. This recipe made the one large loaf pictured, or you could divide it into two smaller loaves.
1. Add 2 1/4 tsp. yeast (one packet) to your mixer using the paddle attachment with 1/4 cup warm water and 1 tsp. sugar. Mix to combine, and let sit for 10 minutes until the yeast froths and expands.
2. Add 1/2 cup sugar, 1/2 tsp. baking soda, 1/4 cup oil, 1 egg, 3 egg yolks, 1 1/4 cup warm water, and 2 tsp. salt, mixing to combine. Begin adding flour about 1/2 cup at a time until the dough forms a ball and the paddle attachment can no longer move it around (about 3 cups). Change to the dough hook attachment, and continue adding flour until the dough no longer pools on the bottom of the mixer (between 4 1/2 and 6 cups total). Towards the end, allow the mixer to run for 30 secs or so between additions until you can tell if it needs more. Knead with the dough hook in the mixer for about 10 minutes. I generally err on the side of kneading for a longer time than shorter, because I don't think that you can "over knead" the dough (although correct me if you've done it!).
From there, follow Tori's directions for rising and braiding. In short, let rise 1 hour, punch down, rise another hour, braid, coat with egg wash, rise 30 min, bake at 350 for 20 min, egg wash, and bake another 20 minutes.
I'm going to try out some methods for allowing the bread to rise the night before and in the fridge for those working who aren't able to stay home all afternoon on a Friday to wait for the dough to rise, and I'll let you know how that goes. At the least, you should be able to freeze the challah after you've braided it, and pull it out of the freezer the morning you'd like to use it and let it rise in the fridge all day.
I hope you'll try out making your own challah when you have the time!