Two words often misspelled or used interchangeably are: it’s and its. I know they sound the same when you’re speaking, but each has its (ha, ha!) own unique meaning when you are writing.
It’s is a contraction, short for “it is”. The best way I know to test to see if this is the spelling you want is to read your sentence out loud and substitute “it is” for “it’s” or “its”.
For example, “it’s time for lunch.” “It is time for lunch” makes sense, so “it’s” is correct in this sentence, not “its”.
Its means belonging to. So when I say, “each has its own unique meaning”, that is correct. I’m talking about the meaning that belongs to each word. On the other hand, “Each has it’s own unique meaning” would not be right, because it doesn’t make sense to say, “Each has it is own unique meaning.”
Bonus tip: Sometimes “it’s” will be short for “it has”, as in “it’s been snowing” meaning “it has been snowing”. The simple test above, substituting “it is” for both “it’s” and “its” will usually tell you whether you are using the right spelling or not; but if “it is” does not make sense and you want to be sure you have the correct spelling, then also try substituting “it has,” just in case.