A couple of years back, I signed on as the third of a writing team working on an AU virtual season 2 of SGA. We planned to write the first three eps and an outline of the overall arc together and then write solo installments after that. I did the organizing, taking the overall short outline of the first ep and splitting it into 21 fully outlined scenes we could divide evenly between us. I know some other people split these things up by each taking a different character POV, or each writing a set amount of words and then handing it back.