I wanted to draw your attention in particular to this excellent post from
Sophie Österberg from Wikimedia Sverige -- she's put together a very frank list of mistakes she's made and what she has learned from them. I highly encourage everyone to read the post and add your own learnings, either through commenting on the blog post or through discussion on this list. I think it would be great if we got better as a community of bravely sharing not only what goes well, but what doesn't, so that we can all learn from each others' experiences and not make the same mistakes!