I came across this really cool Refractometer Spreadsheet at the MoreBeer website. Refractometers work accurately when no alcohol is present. Therefore it is perfect for taking the initial gravity reading of your unfermented wort. However, once alcohol is present, figuring out the gravity of fermented wort usually involves solving some mathmatical equations, etc. Well this spreadsheet does all the calculating for you. Just make sure you put in your original Brix reading from your refractometer. Then as your beer ferments, take your usually readings using your refractometer. Put the brix reading in the chart and the sheet will automatically calculate the specific gravity for you!! No more taking of large samples to measure S.G. during fermentation using a hydrometer. Now you can use your refractometer from beginning to end, with little wasted beer.
Here's the link to the MoreBeer page, it has video as well on how-to use a refractometer. The link for the spreadsheet is below the video.