Thought this was a decent summary: (from Ronpaulforums.com)
The easiest fast way without huge markup for newbies, that I would recommend...
1 Create a new wallet for free at
https://blockchain.info/2 Go to
https://www.bitinstant.com3 Select Walmart in the pay from box
4 Select Bitcoin address from pay to box
5 Fill out the info asked for, use your address from the wallet you created. When selecting amount to pay remember there will be an additional 4 dollars added on.
6 Follow through the prompts and select the Walmart closest to you, it will generate a payment slip with the info you need. It will send the payment slip to your email within 5 minutes, copy the info under zipzap biller info or have the slip accessible on your phone. The amount to pay here is the full amount you will pay at Walmart.
7 Go to Walmart grab a blue moneygram slip. Fill out your info in the top portion, fill the info from the payment slip into the bottom portion.
8 Hand it to the person at the counter and pay.
Bitcoins are automatically bought at current market price on MtGox, and forwarded to your wallet.
Fees with this method, 4% to bitinstant 4 dollars to zipzap.
Alternatively you can start an Mtgox account, go to bitinstant and select MtGox in the pay to field, enter your MtGox account number. You then have Us Dollars in your MtGox account, and can choose when to buy coins based on price fluctuation.