It's a pet peeve of mine when people use "then" when they should be using "than."
"Than" is used in a comparison, such as:
"I ran faster THAN Anne,"
"Man, I would rather have my hand in a can, THAN a tan fan in a van."
"Then" is sequential, such as:
"First, I went to the dentist, THEN I went to lend a hen to Jen."
Hopefully, the above alliteration will help solve the world's minor grammer problems.