Here are a number of sites on writing style:
Irony is an excellent technique in adding humor to writing.
Regarding a writing topic.... the very best topic is a challenge that you have experienced. There is nothing like experience as a teacher is solving challenges. I am sure that you have had to face challenges that at first looked monumental, but after a thought or a suggestions were "duck soup". Others mountains may have taken more than one try before being climbed.
Elements of style:
Scroll down to the bottom of page 1 and there should be things in those lists that will give you a specific idea to write about.