- Good is an adjective, not an adverb. Something does not "work good," it "works well." Native German speakers are forgiven for confusing these, since German adjectives and adverbs have the same form. Everyone else, get it right.
- Lay is a transitive verb. The intransitive verb is lie. And since the people who confuse the two aren't likely to know what a transitive verb is, it's back to Grammar 101: A transitive verb is a verb that takes a direct object. You don't lay down for a nap, you lie down. You can lay your baby down for a nap, however.
- In English, prepositions take the accusative case, not the nominative case, even when the subject is compound and includes a pronoun. What's an accusative pronoun? Me, him, and her, as opposed to you, he, and she. My daughter does not talk to "my husband and I," she talks to "my husband and me" (and everyone else, for that matter). And the phrase is "just between you and me," not "just between you and I." Unless we're speaking Spanish (entre tú y yo), but we're not.
- It's is a contraction of "it is." The possessive adjective is its, no apostrophe.
Lest I become accused of linguistic elitism, let me say that I am quite aware that there are dialects in which the standard rules of English grammar do not apply, and that I do not believe that any dialect is inherently better than others. However, there are certain societal contexts in which the use of only particular dialects is considered acceptable, and should you fail to follow the rules of that dialect, be aware that you will be judged accordingly (and likely, unfavorably). It's a bit like the kid who walks into an interview for a bank job in frayed jeans and an old T-shirt. If he doesn't know any better, someone needs to set him straight. If he knows what's appropriate but chooses to behave differently to make some kind of point, he should be prepared for the consequences.
And yes, I too relax the rules of standard grammar depending on my audience and environment. I'm not a stickler for the use of "whom", and I go with the masses when it comes to eliminating the predicate nominative pronoun in favor of the accusative pronoun ("That's him" rather than "That's he"). We change our language, including our grammar, to create a particular effect (not affect, as in the annoyingly incorrect name of my old hair salon, "A Unique Affect"). But creating an effect requires intention, and that requires an knowledge of what is correct and why.