[Utah-astronomy] Newby-type question

OK, It's time for me to get down to doing something I've never succeeded at before, taking flats. Could any of you experienced astrophotographers fill me in on some essentials? First, I assume you have to take a series of 'em for each image you get; in fact, flats for luminosity and flats for r, g and b. Is that so? How many do you take? Second, how can you take them when it's dark outside and you want to slew to another target? Please give me a few hints. Many thanks, Joe