I think my overall take away lessons are:
1) Keep writing. Finish the stories that you start. I outline, write, and then edit. That process works for me, but I’m sure it is not the only process that works.
2) Send multiple stories out at the same time. Keep sending work out. The more stories that are in circulation, the less any individual rejection will hurt.
3) There is no replacement for a tight match of the story to the submission call, both in terms of following the guidelines, and responding very specifically to the theme if it is for a theme call. I have had the best luck selling stories that were written specifically for a given open call.
4) Tight word counts are your friend. I find that tight word counts teach me to edit my own work better than I would have done without the pressure of the word limit.
5) Learn from rejections. While some come back without much feedback, I always craft a working hypothesis as to why the piece wasn’t a good fit for the publication or good enough, so that I have a vision for the revision.
6) Keep reading. I learn by reading and by writing. If possible, read anthologies by the editor, or magazine issues by the editor. Each time you read a story, think about what worked and what didn’t. This is all in part a matter of taste, but it is definitely part of the learning.
7) Social media is awesome. I think the greatest part of Twitter is the sense of networking with other writers and editors, and the on-going inspiration to keep up the work. Twitter friends, the knowledge that you are writing helps me stay motivated to keep writing.