When I rec a fic, I try to rec fics that I think are flawless, or nearly so. This is because I tend to be very tolerant of stories that hit my fancies. I remember reading (and enjoying) this one story that had questionable plot, characterization, and grammar just because I enjoyed the idea and liked the characters it focused on. I enjoyed that fic quite a bit, and I'd probably consider rereading it in the future. But I wouldn't rec it, because even though I enjoyed it, it does have issues with grammar/characterization/ect.

So, I rec fics that I think are flawless or nearly so. I also rec fics that I figure most people haven't read. I'm not going to rec one of the most read stories in the fandom, I'm going to rec the undiscovered gems. XD

Finally, I like to point out the positive things about the fic. I think I have mentioned the negatives a couple times, but overall I try to send people into the stories feeling that, "Wow, this must be a good fic." ^^