Apostrophe does not mean "Look out! Here comes an s!"
Use the apostrophe when something belongs to someone:
Craft Snark's apostrophe rant
Use the apostrophe when something belongs to something else:
the toy's shelf
the purse's handle
the blog's first post
Do not use the apostrophe when you are just talking about a bunch of stuff:
a room full of Mikes
There is the odd exception because English was designed by people who think it is normal to take courses in your native language for 12+ years in order to be able to get it right. I'm not going to get into those here because as long as you can get this top part right, you'll already be ahead of a lot of people. You're welcome.
Now, go be snarky and leave me lots of comments with mis-used apostrophes. Yes, I know you were thinking it.