If you think your grammar usage is weak, unskilled or just plain uninformed, Stephen King in "On Writing" has potentially good news: Your grammatical skills, learned in middle school and beyond, are already in place. You either absorbed them in conversation and reading or you did not. However, there are ways to enrich grammar that work for any skill level, grammarian or newcomer; these exercises are challenging and enjoyable, especially if you want to enlarge your writing skills and vocabulary.

Diagram Sentences

You strengthen your grammar when you study sentence structure. Visualizing the structure of a sentence shows you how your sentences may need revision; it also reminds you of your old friends -- parts of speech -- and how they function in a sentence. If you master these elements, your writing may improve dramatically, especially your understanding of proper syntax and diction. Set yourself a goal to diagram five sentences a day for a month, then increase to ten. Exercises for sentence diagramming can be found in Stephen King's favorite grammatical reference, "Warriner's English Grammar and Composition," which is also a favorite of many English instructors.

Read and Write

Read and write, all the time: There is no better guideline for grammar enrichment. Reading many books is a natural way of learning various methods of putting sentences together. Any good novel will demonstrate the numerous grammatical choices authors make, and the options available to you; it need not all be "correct." Hawthorne goes into compound-complex sentences describing the river in "Scarlet Letter"; Hemingway writes, in Big Two-Hearted River, this description: "He came to the river; the river was there." Try writing a descriptive paragraph about a setting; see what words and sentence structure you choose as a constant reader.

Pick a Phrase

Pick a particular kind of phrase, clause or grammatical rule to study exclusively for a week -- such as the prepositional phrase, an extraordinarily useful modifying device. Thoroughly study a prepositional phrase's structure: It begins with a preposition and is followed by a noun, pronoun, gerund (really enrich yourself by discovering that wonderful tool, an -ing ending verb used as a noun) or clause. Pepper your writing with prepositional phrases; underline them at first to be sure you recognize and can identify them. Eventually this grammatical usage will inhabit your writing "at home," "in the workplace" and even "while swimming" with the gerund.

Grammar Games

Play grammar games; these are everywhere on the Internet -- yes, there's an app for that. They are playable at any age level -- even high school and beyond -- to strengthen your grammar skills. One excellent game out of many is EC English Language Schools' online review and quiz of homophones -- words that sound the same but are spelled differently -- such as "principal/principle," "accept/except," "affect/effect," and the ubiquitous "their/they're/there." Spelling, vocabulary and grammatical usage are all honed with these cognitive tools.