Just in case you don't think it is important to pack light and carry on, listen to this.
I think the rule of thumb regarding checked luggage should be, just dont pack anything that you cant afford to lose. Simple as that.
Somebody once gave me the best packing advice ever: when traveling, never take anything you will cry over if you lose it. So true.
My philosophy is, take everything you absolutely have to have and pack it in a carryon bag, paying attention to the weight (the airlines limit and what you can carry). Take everything you don't absolutely need, but might want, and put it in a suitcase, to check. Then, assume the airline will lose the suitcase and you won't have it anyway, and leave it home.
You may be carrying something that must be checked. My husband returned from a trip to Africa minus an $18,000 item. He flew Delta & a Delta affiliated airline. Luckily, he insured the item for the trip because he recovered very little from Delta. Also, three people traveled together each with 2 pieces of checked bags. By the time they got home, 3 pieces were missing, one showed up the next day & another within 6 weeks. If you can't carry on, insure.