"Look," Alex said furtively to Patty, as the teacher droned on. "Who are you going to take to the dance?"
"Don't know," Patty shrugged, twirling a pencil between her fingers thoughtfully. "Haven't decided who to ask yet."
"Well, I hear the janitor's free," Carlos said from behind her, smirking malevolently. "You could always ask him."
"Ahahahaha," Patty laughed in a forced-sounding way.
One common mistake writers make is falling into patterns. The story that inspired this kept writing dialogue the same way every time.
"First part of whatever is being said," character said adverbly, as they and/or someone else did several different things. "Second part of statement."
This would not have been so bad if they didn't over-write, if they had just stuck to the meat-and-potatoes version;
Character did something indicating their emotions. "First part of whatever is being said," character said. "Second part of statement."
Or if they had mixed it up a little. The meat-and-potato