Hydrometer Usage
Using a hydrometer is pretty easy. The hydrometer will come in a plastic tube. To measure the SG of a liquid: take the hydrometer out of the tube, fill the tube with the liquid, and then (over a sink) put the hydrometer into the tube and splash a little more liquid out after it's done overflowing. When things quit splashing around and the hydrometer quits bobbing up and down, read the number off the scale on the hydrometer where the liquid meets it. There may be multiple scales, but the one you want is the one that goes from about 1000 (or 1.000) at the top to about 1150 (or 1.150) at the bottom. If you've filled the hydrometer tube with water to see how it works, it should be very near 1000. (It won't be exactly 1000, because your water will probably have some gases dissolved in it, won't be the temperature the hydrometer was calibrated for, etc.) When measuring gravities of beer/wort, wine/must or mead/must, you should read the manufacturer's instructions and try and get things near the temperature they specify. Also, if you're measuring a carbonated liquid, let it sit long enough that it's gone entirely flat. Put the cap back on the hydrometer tube and shake it some, even. That's it.