Deciding which to write first?

I tend to start writing each story and just keep going back to each one as I get more ideas. One problem though is that I forget what I wrote for each story, probably not a good thing.
Whichever works for you I guess.

I've done this a couple different ways.

-Work on both. Have a set word count for both, and write toward it each day. So, for project one, my word count goal might be 750 words (or 3 pages). I'd work on that in the morning. For project two, my word count goal might be 2500 words (10 pages), and I'd work on that in the evening.

-Work on both, with no set word counts. Just work on whichever one calls to me the most at the time.

What usually happens with the second scenario is that eventually I get more interested in one project than the other, and focus on it.

But YMMV, of course.

I write whichever one is on my mind the most, prompting the most ideas etc. If I start getting stuck, I'll turn to another and start on that, and then return to the first with fresh eyes.

I am currently writing two different books at once, and it's difficult. That might be because the content is so different and the fictional worlds are polar oposites. That sounds like it should be easy to revert from one to another, but it's difficult for me because the writing style is slightly different and I have to put myself on a totally different track. I've basically decided to bring my 4th book to a halt while I finish up the last of the 3rd, THEN continue my 4th (hopefully by the end of the summer). The downside to having made that decision is that most of the inspiration for the 4th book has faded. I wrote a complete outline for the book, but it can be difficult to resurrect a decaying idea.

You know yourself, JJM. I suggest that if you can write two stories at once, then do it. But if you can't, then both books might suffer, as was the case with me.

I often write two stories at once. Eventually, I get caught up in one of them and finish it, then get back to the other. For me, that's the best way to make a decision--either write the one I feel the most passionate about, or if that's not clear, write both until I discover which one I'm most passionate about right now.

I had this problem too. I had two stories that were supposed to be linked only by setting. I had planned out both of them quite well and was also having trouble deciding which to write first. After a quick draft of the first chapter for both stories, it was pretty clear which of the two I was more inclined to write. Some ideas, though they work out great in your head, are not nearly as dazzling on paper.

As soon as I get a general idea of a story, I start outlining it on a slip of paper, which I then store in a secure place. Though I try not to, I usually can't resist starting the acutal writing process as soon as I get the opening lines. This means I'm usually writing multiple stories at once (at a guess, I have eight stories being written right now, including one novel and not including a few stalled WIPS). The problem is that as I grow older and busier I have less time to dedicate to writing in general, and that gets worse when I have to divide my attention between projects. I'm trying to learn to let outlines be outlines. If they're good, the muse won't be able to resist writing them one day. If they aren't, I haven't taken precious time from better projects for them.