Gets molested in a crowded train but keeps quiet about it.
Stands in rain for 5 minutes. Gets sick for a few days.
Is with the seme/uke. Is about to confront or get confronted about something. Runs away at 100 mph instead. Seme/uke chases.
"Are you fine with me? But I'm a guy," (No shit sherlock. You're boh guys)
Inserts dry finger. Seconds later panel shows a wet sticky asshole. (How? Or is that diarrhea?)
That's all I can think of at the top of my head.
One of them is really clingy with the other, most of the seme is the clingy one, and the other students notice and either tease them by calling them homos, or are just like "you're super friendly today too!" And then the one being clinged onto, often the uke, is all embarassed and starts avoiding the seme, either because they're afraid of their relationship becoming known, or they just don't want people to start badmouthing the seme and accusing him of being gay. Even though he is.
Also the whole, "omg a girl is confessing to him, she suits him better anyway!" and then they congratulate the seme and are all "you should go out with her!" And then the seme either is like "what's wrong with you." or goes like "ok." and the uke is all bitter and depressed until the seme is like "I lied~ I knew you'd be jealous."
let's gather the most common cliches in this kind of yaoi
lemme start:
the main character is asked to go out with his friends/classmates to karaoke but he refuses and tells them he has no time for such an activity even though he won't do anything after school anyways