Its versus It's rule: it's an easy one to follow once you understand its usage.

It's versus Its.

One simple rule: use the conjunction when you mean: it is. Otherwise, it is (it's) just "its".

Examples:

• It's a strange world out there.
• Its bark is worse that its bite.
• It's a clever dog that can scratch its fleas.
• It's time to come inside.
• I can never tell if it's going to rain.
• Put that remote control back into its holder.

Even though it is the remote's holder, the "it" in reference to the remote does not take a possessive apostrophe.