My daughter knows I read yaoi (she's 15) and I recommended http://www.mangago.me/read-manga/love_me_baby_sasamura_gou/ . It's shounen ai and told her it was up to her if she wanted to read other kinds of stories. So if recommending BL I'd go with shounen ai first. If other kinds like shoujo I'd recommend http://www.mangago.me/read-manga/dengeki_daisy/. I guess it's up to how well you know your friend... ╮( ̄▽ ̄)╭
what would be the first manga you'd like to introduce to a friend?