I've made several batches of root beer, and I think it's high time someone made an open-source recipe for everyone to follow.
I'm going to post my next batch ingredients and process here, please feel free to contact me and send me your recipes or modifications.
Typical ingredients I use
Root beer extract as a base flavor to start with Spearmint leaves Nutmeg Licorice (the real stuff, from Italy, not the candy crap) Maltodextrin (makes a good foamy head) champagne yeast honey or sugar for sweetness
Typical instructions
put spearmint leaves in a teaball and drop it into a large pot of water heat water until it turns green and releases a nice spearmint smell add nutmeg the same way, let flavor steep in add licorice, let it dissolve (be careful, it's real easy to overpower the flavor with this!) add honey or sugar for sweetness let water cool to lukewarm temperature add maltodextrin and yeast, bottle immediately.
Get the reusable glass bottles with the ceramic closures, they're great. Make sure you have a couple 20oz plastic pop bottles, fill them to about 1.5" from top. You can test the carbonation by squeezing the plastic bottles, when they're solid, open one up and taste it. If it's still not quite there yet, wait another day and try the other one. Depending on your ingredients, room temperature, and other factors, the carbonation process can vary greatly. Typically take 3 days to make a good carbonated beverage for me.