I had horrible grammar for about half of my life. I just didn't care about it. But then I moved to a country, Latvia, where I didn't know anyone, I couldn't speak the language, and it was too cold to go outside for about 10 months of the year. I had to find ways to occupy myself during this time, so I took on various projects: I worked out every day with a bunch of bricks that I tied up inside the dismembered legs of an old pair of jeans; I forced myself to do everyday chores left-handed to improve my ambidextrousness (this is still paying dividends, by the way;) I concentrated on improving my handwriting; and I read all the time. All. The. Time.
As soon as I walked in the door of my crappy apartment I'd grab a book and start reading. I'd cook while reading, I'd read while doing sit ups, I even made a book holder so that I could read while I sat in the tub washing my socks. (Provided it was the weekend when the hot water was turned on, that is.)
Eventually, I decided to read with a purpose. I assigned myself various reading projects: One of these was to read the works of Charles Dickens all the way through in chronological order without stopping; another was to read all the original major monster books--Dracula, Frankenstein, The Invisible Man, Jekyll and Hyde, etc...--to see how the legends began; and still one more was to figure out how grammar worked.
Here are a few things that I didn't know before I decided to just learn them. Memorize these rules once, and you never have to learn them again:
1. The apostrophe never makes a plural. It's "moronic tattoos" not "moronic tattoo's," "shitheads" not "shithead's."
2. When trying to figure out when to use "me" or "I," simple isolate yourself in the sentence. So, let's say your bro Mark is going with you to the tattoo shop to support you as you get the world's illest-advised tattoo on your ass. Is it, "Mark and I are going to the tattoo parlor so I can get the world's illest-advised tattoo on my ass?" Or "Mark and me are going to the tattoo parlor so I can get the world's illest-advised tattoo on my ass?" Well, just take your bro Mark out of the equation. Would you say, "I am going TTTPSICGTWIATOMA?" Or, "Me am going TTTPSICGTWIATOMA?" Obviously, the former.
A lot of people who never learn this trick default to "I" in all cases because they think it sounds more educated-er. I find the opposite to be true. Therefore, when a "me" is called for, it's even more important to use this trick. Is it, "The illiterate tattoo artist greeted my bro Mark and I at the door?" Or, "The illiterate tattoo artist greeted my bro Mark and me at the door?" Again, leave bro Mark out of it. Would you say, "The illiterate tattoo artist greeted I at the door?" No. So me's the way to go in that case. (By the way, I know you would never leave your bro Mark out of your plans. He's a god among bros, bro. It's just an example.)
These rules are pretty simple. Once you learn them, you don't have to think about them again and asinine ass tattoos can be easily avoided.