You'll get several answers, I'm sure, but here's my take on it.
If you don't tell your broker which shares to sell, then you'll take your cue from the sales schedule which will come with next year's K-1. That's just the beginning however, and you'll have to deal with the issue of partial sales. You won't be able to use any of the deferred expenses you've been accumulating because you can use them only on a complete sale. You can still carry them forward.