Post links to interesting videos or sites you've found on the web. It's great to share these things with your friends. Don't worry if they've already seen them; as with most viral content, if you've seen it once, scrolling past it a second time is no big deal. Remember to Like posts that entertain you, too; this improves their likelihood of showing up in Facebook's 'most relevant' list.
Don't steal wilfully
Sharing isn't available on the iOS version (you'll have to go through the web to do that), but copying and pasting other people's posts is very poor etiquette. Like them, and mutual friends will get a better chance to see them. It's the nice thing to do.
It's the little things that matter. Learn about them Facebook is full of complex terminology, but it's mostly straightforward...
Your iPhone can tell where it is based on nearby Wi-Fi networks and mobile phone masts, and by using GPS, but you can turn it off for privacy, or to give your battery a little more juice.
The web version of Facebook includes a function that allows you to point your friends to posts made by other people who might not be on their friends list. At the time of going to press, it's not included in the iOS versions, but we assume it's coming soon.
A profile is Facebook's collection of your personal information. It can be used by potential friends to seek you out, or by Facebook to target advertising directly at you. It doesn't share your specific details with advertisers, but they can use them to build up an idea of what you might like.
Wall / Timeline
The wall was Facebook's first big innovation. Basically a message board, it gave you an place to scrawl your thoughts, and other people could come along and do the same. This has morphed into the Timeline; your page will still have a 'wall' type area on which friends can write messages for everyone to see, but it mostly consists of your status updates, events and milestones.
Pages / Groups
Pages are like profiles, but for businesses or products. If you've got something to promote, a page is the best way to do it - you won't fill your own timeline with advertisements, and your page is open for anyone to see. Hopefully your personal profile won't be. Groups are essentially discussion groups - think of them like book clubs.
Got nothing to say? Want to give a post some props? The 'Like' button is for you. It's analogous to the Facebook 'poke', in a way: an action you can take to tell a person you've noticed them, without the explicit requirement for words.
A like can have the side effect of telling people on your timeline that you've liked something, but it doesn't always.