Word Trick ( It's vs Its )

Here is another confusing pair It's and Its

It's

It's is a contraction for it is or it has.

If you can replace it [']s in your sentence with it is or it has and if it makes sense then your word is it's.

For example:

1.  It's been good to know that.  Contraction: It has.

The sentence will be: It has been good to know that.                                   

2.  It's a x-ray machine.  Contraction: It is.

The sentence will be:  It is a x-ray machine.

Its

Its is a possessive pronoun meaning, more or less, of it or belonging to it.

Its is the neuter version of his and her. If you try to put the her or his into your sentence where you think its belongs and if the sentence works grammatically then your word its.

For example:  

1. The cheetah is well-known for its ability to  run fast. Possessive pronoun: its ability = the cheetah's ability.

And there  is no word such as its'.