I have a few
-The Uke casually overhears a conversation that the Seme is having but only hears halfway and missunderstands.

-Uke falls in love with that guy who pick up their something and give it to them.

-Always thinks the guy he likes should marry and suffers for it.

-Cliche school setting and one or both protagonist are the most popular in school.

-At least 75% of all yaoi guys claim to be straight.

-Have sex in the first chapter (second at most).

-Uke is the small cute and younger one. Seme is the tall, good looking one.

-Sometimes the Uke is older and the seme is younger. (Wish there was more sekes)

-The stupid lightsabers that ruin the "sexy" scenes.

-Usually the Uke's hair color is lighter than the Seme. (because is manga I meant white.)

-They have anal almost immediately without preparation.
(I know we're horny and we want it soon, but the wait is what makes it exciting, right?)

-The Uke thinks the Seme is like a dog.

-The "I just heard something awful and run away like a little kid without being reasonable despite people asking me what's wrong"

-The super cliche Seme actitude. That one that makes you think he knows it all and is ready for everything.

-The mega cliche Uke actitude. Naive, innocent, always nervous around their Seme.

-Tsunderes... xD

-The guy that run away from their lifes because... reasons, and for some reason that one guy who is the reason they run away appears out of nowhere.

-Miai or omiai, which usually are force to the characters by their parents.

I could keep going. So just put anything you can think of xD