1. Use Saran wrap to keep shampoo and other liquids from exploding in your checked luggage. Unscrew the tops . . . put some plastic wrap over the hole . . . and then screw the top back on. It just adds one more layer of protection.
2. If you forget the little brick plug for your phone charger, check the back of the TV in your hotel room. A lot of hotel TVs have USB ports now. Or just call the front desk and ask to borrow a charger while you're there. Decent hotels usually have a few.
3. If your flight doesn't have TVs in the seats, improvise. You can watch something on your phone hands-free by putting it in the plastic barf bag they give you, then hanging the bag on the little latch that holds your tray table up.
4. Use a belt to keep the collar on your favorite dress shirt from losing its shape. When you pack, roll a belt up, and put it inside the collar so it holds the shape of your neck. Then pack something tight on top of it, so the belt doesn't fall out.