One of the smartest little tools I ever purchased was a luggage scale. I am not a "pack light" kind of girl. I like to have the things I need and enjoy with me when I travel... so I have a wonderfully large suitcase.
Tip #1: Ideally, and whenever possible, I fly Southwest so I do not pay any luggage fees.
Tip #2: Whenever I fly (paying for luggage or not) I get my money's worth by taking the entire 50 lbs - without going over and paying the extra fees. This is where the luggage scale comes in! If by some fluke I still have some extra needed weight to hit the 50 (or 49.5) mark, I add a bottle of wine (wrapped in bubble wrap and plastic) or bottled water - both items that save $ on the other end.
Tip #3: I only buy luggage from LLBean because they stand behind their products. I have had numerous pieces replaced, and that gets my vote.