If you really want free BTC, you should go for faucets. There are several of them. Just search on google for 'BTC faucet' or 'bitcoin faucet'.
There is also the option of gambling, but in order to do that, you first need to buy BTC.
Faucets pay so very very little. You can in most cases hope for a few cent's a hour. It is sad, but it's true.
I suggest finding a signature campaign and joining it. It will pay better then facet and also you would be posting anyways so win/win. Just don't spam is the biggest thing.