This is a simple "duh" tip but it was a light to me and I thought I would share it!  I like using broth to cook with but do not use it enough and often my remainder becomes questionable before the next use.  You can easily portion broth in ice cube trays, freeze and then store the cubes in a zip lock bag in the freezer. They allow you to cook while dropping in small enough increments as you monitor the flavor.