I've seen the meme going around where you quote the first lines of your 21 most recent fics. Results below. This is a pretty broad mix, with lots of SPN and SPN RPF but also some BtVS and Downton Abbey thrown in, plus a Yuletide fic.
Generally with first lines I want to give convey setting or character or era (if canon-fic) or conflict or, ideally, all of the above. Most of these do at least one of those things. I also tend to start things with context-less statements that I then interpret in the next paragraph or so. Otherwise, I'm not seeing a lot of patterns here.( first lines )
OTOH, I decided to list my last lines as well, and wow am I confirmed in my impression that I was weaker with endings than beginnings. First, lots of dialogue, which is not necessarily a problem in itself but which probably should not end every
story, and second, a lot of sentence fragments that make no sense out of context. Hmph.( last lines )