Picking lemons/limes/oranges/etc.

Two of my friends recently got me a cooking class for Christmas (they know me so well!)  We met the instructor at a farmer's market and we each purchased several items from the stands based on the recipes that the instructor had selected for the class.  One of the items on our lists was to pick several lemons and I learned something from the instructor about how to pick them.  She told us that you want to pick lemons that feel heavy for their size because it means that they have a lot of juice in them.  I've used this advice since that day and have to agree that it's a good way to pick lemons, so now I'm sharing it with you.