I bought some bitcoins from a friend, I don't even have a wallet, now what? I bought $10 worth of Bitcoin from a friend that does Bitcoin mining, but he told me I need a wallet so he can send them to me.

So how do I create a wallet and what information do I need to email to him so he can send those bitcoins to my wallet?
The two most common options for wallets are:

Online wallet 


You basically sign up on a website such as Coinbase(recommended if you are in the USA), or Bitstamp( recommended if you are in Europe). There's also other options like: Mt.Gox, BTC-e, BTer, etc. There you should find an option to "Deposit funds" using Bitcoin, which will show you your wallet address. That is the address where your friend should send the bitcoins to.
Pro's: the third party website maintains your wallet synced for you, everything is based on the cloud, so you can operate from any computer.
Con's: the third party is essentially in charge of your money, so you have to trust them


Local wallet. 


You download a software ( official one is here). Install and run it. Once you run it, it will take a from one to few hours to download all the blocks from the network.
Pro's: you don't need to trust any third party. So, unless someone accesses your computer somehow(i.e. physically, malware,etc). You are the only one in charge of your money
Con's: if you loose your wallet file(i.e. stolen computer, damaged hard disk,etc), you basically loose your money( unless you kept backups of your wallet). You can't operate in all computers, although you could in principle have your OS installed in a memory stick, hence being portable, and at the same time risky.