as27605, you get bitcoins by selling something that somebody wants (like USD) in exchange for them, in a market. There are several ways this can happen, but most (if not all) of them require you to establish some form of identity. This identity might have nothing to do with your Real Name or forum name -- it typically corresponds to a GPG keypair when trading on IRC.
Alternately, your identity can be a user account on a trading website such as TradeHill.com. If you want to easily buy and sell BTC, you'll need an online way to send USD. Currently "Dwolla" is popular for this. Paypal is frowned upon, since transactions are reversible.
One popular "over the counter" market is available to you via the #bitcoin-otc IRC channel on freenode. See this webite for more about that method:http://bitcoin-otc.com/
Note that you'll have to be comfortable using IRC. It helps tremendously if you're familiar with GPG too. Remember that your IRC nickname is different from your GPG identity -- you link them them you authenticate with "gribble" -- the bitcoin-otc bot. You should ensure that everyone you deal with OTC is authenticated with gribble and has a good trust rating.