There are some pages that I really like following, because I feel that they make quality posts, and I want to help them out by liking their posts. However, I do not wish my friends to see that I have liked their posts.
I understand that friends will be able to see the posts themselves and thus see that I have liked them; that's fine. I just don't want it to appear on my friend's news feeds.
This also applies to photos I'm tagged in, and posts that I comment on.