Sharon Laudenbach, President of LuggageOnline/Robinson Luggage shows how you can pack into one suitcase in order to save on second checked bag fees. Overpacking is the biggest mistake that people make. So here are some important tips that Sharon suggests:
With all the fees that airlines are charging and beginning to charge today. Why pay for overweight fees too? This article has some good advice on why you might just want to purchase lighter weight luggage to begin with. You might agree once you see how much overweight fees can be! There are many brands that are meeting the needs of travelers and going to lightweight, lightweight, lightweight! The article mentions a few, such as Eagle Creek, Victorinox and Briggs & Riley. Don’t worry these lightweight bags are just as great quality as those heavy bags that you’re carrying now. Good Housekeeping Research Institute tested the bags and you can read more about their findings by reading the full article.
You might even want to get your own travel luggage scale. I use mine before I go on every trip and I even bring it with me in my carry-on, because I always tend to bring back extra things on the trip home. If you use a scale when you’re done packing, you will know whether or not your bag is overweight and you can take things out or rearrange your bag. This way you won’t be surprised with any extra fees when you get to the airport and we all know that we don’t want any more fees than need be!!!
See here an example of a luggage scale for purchase at luggageonline.com:
by Dana Walsh, Director of Marketing & Recruiting · August 1st, 2008 
