Although I lost track of how many times I've tried to learn this topic, it´s hard to use it properly, don´t you agree with me?. Hence, anytime I find something related to it, I try to master this, once and for all. :)
This infographic is my suggestion for today. It's an amazing material from "The Oatmeal". So, let´s go! Click on here and have fun.

update: I´ve got an import comment from a native speaker about this topic on my Facebook page:

Patrick Hill To who are you speaking? Ha! The article says whom adds no effect or clarity to the language? Wrong. An educated speaker of English would notice if you didn't use whom and judge you accordingly. Just because many Americans don't get it right doesn't make it correct usage of the language. It's not a word to be discounted outright in spite of our many trends of bad English. "May I please speak with George?" (response) "This is him." (Corollary to whom) Wrong. 
"This is he." Correct! 
If there is an incorrect way there is also a correct way. Don't take the easy way out of mistakes with language. People who know better will notice.

Danniella Nascimento Ohh.. thanks a lot, Patrick. It´s really important to have an opinion from a well educated native speaker. 
Just as in English, this also happens in Portuguese. I mean, we have words or expressions that are considered right only because of the usage, even when they are wrong. However, it´s not good when some of them are used in a heavily wrong way and people who know what´s correct, can notice it. They can wrongly judge you by how you speak the language. I got it.  

Thanks again for you comment and feel free to make others, whenever you want . It´s always welcomed.