Make a Yeast Starter for Successful Fermentation

From Bryce Eddings, former About.com Guide

Consult the temperature recommendations on the yeast package. Cool the wort to your target temperature. If you’ve harvested yeast from a previous batch or a bottle and don’t have the original manufacturer’s temperature recommendation for your yeast, shoot for 60 to 72 degrees Fahrenheit for ales and 46 to 55 degrees Fahrenheit for lagers.

Make sure your keep the lid on your sauce pan except when checking the temperature to keep out contaminants. Also make sure your thermometer is sanitized before putting it in your wort, see the next step.