It's obvious when you think about it, but it might not occur to you when you're rushing to try and fit everything into your case ahead of a big trip: if you're running out of room, slamming your case on the floor a few times can help settle the contents.
Picture by Tom Godber
Lifestyle site Martha Stewart offers an in-depth guide to packing for business trips, which frankly involves more effort in keeping creases out of clothes than I would generally bother with. But it does include a useful tip for increasing space:
If you run out of space in your bag before you've packed everything, there's a way to get more in: Drop the bag on the floor a few times, then open it -- things will have settled, and you'll find extra room.
Obviously, proceed with caution if you're travelling with a lot of gadgets, and bear in mind that folding your clothes, even if they're technically "dirty", is more efficient than just shoving them in. And remember, you can get by for long periods without packing too much stuff.
Packing a suitcase [Martha Stewart]