I've said it before, I'll say it again: do not pack valuables in a checked bag. Put them in a carry-on, or better yet, on your person. Best of all, leave them at home. Here's why: many airlines officially don't accept certain valuables in checked bags. Sure, people still pack these things, but if anything happens to them, it's not the airline's problem.
And you might be surprised to find out what's considered a "valuable" they won't cover. I'm sure I don't have to tell you that jewelry and electronics are, but so are the following items according to American Airlines' contract of carriage (and other airlines have similar restrictions): books and documents; computer software; eyeglasses, sunglasses and contact lenses; furs, keys, medicines, cameras and cash.
Same for heirlooms, so leave great-grandmother's homemade quilt home, too. If it gets lost, you won't be compensated.
And by the way, per the Department of Transportation, airline liability per bag is only $3,300. That could be the price of one good camera, if such an item was covered. And, as noted in the DOT's "Consumer Guide to Air Travel", "Airlines consider the depreciated value of your possessions, not their original price or the replacement costs."
This could be where your credit card comes in handy. American Express, for example, offers some additional checked-bag and even carryon insurance coverage that does cover valuables, and your homeowner's policy is worth a second look. Many airlines offer additional coverage as well. No matter what you do, though, please read the fine print.
Let me repeat: do not pack valuables. If these are must-haves, why not ship them via UPS or Federal Express? Just be sure you know what compensation the shippers offer should any of their packages go astray.
#4: Do Not Say, 'I Don't Know What's in My Bag'
If your bag is lost, the airline will want an itemized list of what was in it (another good reason to pack light).
The more detailed you are about the contents (and the bag itself), the better. Include clothing sizes, colors, types of shoes, that sort of thing. And you know that all black bags look alike, so take a picture of it with your cell phone. And while you're at it, take a close-up picture of your baggage claim tag, in case you lose the little sticker they give you.
I've heard that some people who travel a lot create a packing list template that they use for a quick reference when getting their stuff together; this would sure be a handy reference to have when filling out those tedious airline claim forms.
Finally, make sure you have a legible ID tag, outside and inside your bag.
Your airline is supposed to stay in touch with you, but if not, be proactive and be polite. Reference your official lost bag claim number in all correspondence and if you are using e-mail, be brief and to the point; include all pertinent information such as dates and flight numbers. Stay on the case.
If worse comes to worst (and you're feeling especially creative), you could do what Dave Carroll did and create a music video that becomes a YouTube hit. (Surely you remember "United Breaks Guitars"?)
Or do what I do: I never lose a bag, because I never check a bag. With me, it's a carryon all the way. However, if I did ever lose a bag, I'd be tempted to visit an Alabama store by the name of Unclaimed Baggage Center.