If you have made your Facebook profile public and post publicly, you will have realised that nearly anyone and everyone can comment on the stuff you post. If you would like to adjust the settings so that only your friends can comment, but anyone can like the stuff you post, follow this simple tutorial.
The main reason I have enabled this on my profile is because I have subscribers who comment on my stuff in a whole different language which can be quite annoying.
1. First you need to go to your account settings. You can access them from the little triangle, at the top right of the page, next to the Home button.
2. Once in the account settings, you need to hit the "Subscribers" tab which is on the left side of the page.
3. You will then see a section called "Subscriber Comments" - just change your settings there. I've chosen friends of friends but you can choose to have your subscribers comment or only your friends.