Use it's (with the apostrophe) only when you mean "it is" or "it has." For example: It's time to go. (It is time to go.)It's been a long time. (It has been a long time.) Use its (without the...
This depends solely on which pronoun is used prior to the verb "to have".
I am
you are
he/she is
it is
one is
we are
they are
You will need to memorize this as there is no rule to explain...
'I' is the subject of a verb, or the complement of the verb 'to be'. 'Me' is the object of a verb.
Examples:
I am his mother.
I don't know if I will want to do that.
Can I take the dog for a...