I went on a moss walk this morning with the CA Native Plants Society. A friend recommended it after I posted a pic of what I thought was a moss a few weeks back (it was actually a leafy liverwort in the genus Porella), and I knew absolutely zero about mosses, so I joined up. I now know the following things about mosses:

1) They are very small
2) There are a lot of them
3) Did I mention they are small?

Ok, I learned a whole lof of other things, like terminology and what features you should look for to begin making an ID. The instructor showed us a bunch of different mosses, but I figured I would try to memorize one common one, and this is it: Atrichum selwynii. It grows on soil, the leaf is relatively large, the costa (midrib) is obvious and extends to the end of the leaf, the leaf has serrations you can see in a hand lens, and the leaf has a wavy pattern that you can see with the naked eye. It was also all over the place in Huckleberry.