Just like physical exercise, a writing exercise is most beneficial when it is consistent and fits your needs and your lifestyle.
Using a journal to be a better writer is a great way to enhance your skills, and improve the depth of your book.
Review the book that you have just read, not the one that you wish the author had written.
Here are a few tips to get you over the hyperbole hump and onto the meat of the story.
Aspects of the Joy and Difficulties of Writing
Five Pieces of Conventional Wisdom I Should Have Taken to Heart