Remember learning grammar in grade school? OK, so maybe you’re a little rusty. Mistakes like these are common:

Should have/ could have/ would have
Incorrect: I should of applied for Impact Engine’s next class.
Correct: I should’ve applied for Impact Engine’s next class. 

Intents and purposes
Incorrect: For all intensive purposes, Sally ‘s business philosophy mirrored that of Apple.
Correct: For all intents and purposes, Sally’s business philosophy mirrored that of Apple. 

Who/whom
Incorrect: Whom presented at Technori Pitch last month? The Moxie Award for best beard was presented to who?
Correct: Who presented at Technori Pitch last month? The Moxie Award for best beard was presented to whom?

Nip it in the bud
Incorrect: Jim nipped the software problem in the butt.
Correct: Jim nipped the software problem in the bud.

Me/I
Incorrect: Max and me went to Built in Chicago Launch last month.
Correct: Max and I went to Built in Chicago Launch last month.

Couldn’t care less
Incorrect: I could care less about what color the logo is.
Correct: I couldn’t care less about what color the logo is.

Lay/Lie
Incorrect: I’m going to lay down for a nap between meetings.
Correct: I’m going to lie down for a nap between meetings. 

If you’re still not sure why those sentences were incorrect, no need to fear – Mental Floss is here! Whether you can’t remember which weather to use, or when to use whom instead of who, watch this video for a crash course on grammar and spelling. 

[youtube http://www.youtube.com/watch?v=hRMRCeQBAKI?rel=0]