Login to FB and click your name so the page redirects to your wall/timeline. Once there, click "activity log".
When you click that you'll see in the left sidebar a list of options to choose from
From here, click on "All Apps". You'll see all the FB apps you use, down the middle of your screen. Now here is what you might not know - it seems all these apps have a default setting to show all your friends you're using them. Which is fine, if you don't care who sees what. If on the other hand, you don't want to flood your friend's newsfeed with everything you're doing on FB, or if you're using an app that you don't want anyone to know about (for example, an upcoming surprise for someone or if you're just testing it out to see how it works or even if you like it), you need to select the app and adjust the settings:
I selected my twitter app for this and as you can see, it's set to show all my friends. On your page, click the button next to whichever app you want to adjust the settings for:
And then select who you want to make your activity on this app available to. I don't have a lot of apps on FB but you might, so scroll down the page to view the settings for all of them and adjust them accordingly.
Here's another FB setting you might not be aware of. Facebook "privacy" is pretty much a joke, but there are things you can adjust to keep your info a little more to yourself. On your main page (your newsfeed page) you'll see this in the top bar:
Click the little gear icon and scroll down to privacy settings. Click that and you'll see this in the left sidebar:
Click on Apps and read this very carefully under your list of apps:
Click the edit option to the right of this paragraph and be prepared to be surprised at how much of your info is being shared by your friends (bless their hearts, lol) whenever they're using different apps on FB:
The copy here says it makes your friend's experiences better and more social. What they really mean is, your info is being plastered all over FB whether you like it or not, because your friends are using certain apps. I was surprised at all the categories that were checked when I first looked at mine, so I unchecked them all. What you choose to allow is up to you, just be sure you hit SAVE CHANGES when you're done.
Hopefully this has been helpful.