Ludwig Wittgenstein's primary philosophical focus was on language, and for good reason. Language is how humans express ideas and communicate, and it is important to do so effectively. Based on his ideas and my own, here is a rough guide to using language effectively:

• Know its Limits: One thing Wittgenstein is well-known for is viewing all philosophical problems as essentially failures of language; there are some fields where language is simply insufficient to address a question. I'm not sure if I agree that all philosophical problems are like this, but it is nonetheless important to recognize when an idea simply can't be expressed via language. At that point, it may be best to resort to other mechanisms, such as illustrations, or to simply shelve the topic altogether, since you'd just be wasting your time.
• It is Defined by its Speakers: Language has no inherent meaning, and exists only as a common code, where certain symbols encode agreed-upon meanings. Thus, as Wittgenstein states, there is no private language; it only exists with reference to others. Thus, the most important thing when using language is to keep in mind the audience, rather than simply spewing your thoughts as words that you understand, but they may not.
• Pragmatic Usage: The "correct" use of language, according to William James's "Pragmatics," is the usage that has the desired effect. Basically, as long as the language you're using has the effect that you want, it doesn't matter whether or not you end a sentence with a preposition. In most cases, the desired effect is to communicate your ideas effectively and concisely, without looking like a buffoon. Following recommended usage (such as commonly-used spelling and grammar) is usually in line with those goals.