Buying and selling bitcoins (BTC) is not that terribly difficult but it can be a bit confusing for those folks who are new to the bitcion world or alternative currency. If your looking to sell your bitcoins then you obviously already have some bitcoins on hand to sell and your probably already familiar with a bitcoin wallet where you would keep your bitcoins stored. Then again, you might simply have all your bitcoins sitting at a bitcoin exchange like Mt Gox or BTC-e.
The easiest way to sell bitcoins is to find a buyer, exchange cash and simply forward to bitcoins from your wallet to theirs. You can find local buyers through bitcoin exchange groups via message boards, forums, craigslist and even eBay. There are quite a few web sites online that focus on finding local bitcoin buyers and sellers for the sole purpose of selling and buying bitcoins.
The most popular and probably the safest method of buying and selling bitcoins is via a bitcoin exchange like Mt Gox or BTC-e. These exchanges are easy to setup an account with but not always easy to link to your bank account. There are quite a few hoops to jump through in order to be able to transfer funds or cash to and from your bank account to these exchanges. Its easy to transfer bitcoins from your bitcoin wallet to and from these exchanges but not so easy to transfer to and from your bank account.
I would recommend setting up an account on both MT Gox and BTC-e just to get a feel of both and see which one you like best. I would then go through the process of connecting both accounts to my bank account or some account for which you can send funds to and from. All the while you might try some local bitcoin selling and buying by finding a local bitcoin enthusiast. I would start with a small amount at first to get comfortable with the process before making any large transactions.