Get off of my lawn!
All of my children are studious.
Half of the profits are yours.
All those sentences – note that I didn’t say all of those! – can be rewritten without the word of.
This is a hard rule to remember. What I do is write whatever comes into my head and then when I’m rereading and revising my material, I go back and look for the number of times that I used of.
Of course, sometimes of is essential. Here are sentences that wouldn't make any sense without it: "The floor is made of pine wood." "The dog is tired of his regular biscuits." "I'm writing a book composed of grammar tips." Those sentences all require the preposition of. So, use your good judgment and double-check your work to remove filler words like of.
Sigrid Macdonald is the author of three books, including the Amazon bestseller Be Your Own Editor, available on Kindle as well as in print. http://tinyurl.com/6oobf97 She is also the winner of Grammar.net’s Best Grammar Writing Tips Blog of 2011.