When getting off a bus at a major tourist attraction in India, forge ahead and try not to make eye contact with the vendors who will swarm you (unless you really want one of those trinkets). Sometimes, the vendor will try to place the object on your body, thinking that once it is on you, you have to purchase it. Just brush it off and go on your way.
When traveling internationally, take along a roll of toilet paper. It compresses more than you think, and you never know when you'll be using some primitive facilities at a historical sight.
When going on a tropical vacation, always pack a swimsuit in your carry-on luggage. If your suitcase doesn't make it, you can still hit the beach. I once spent my first few hours on an island swimsuit shopping. Not my idea of fun!
If at all possible upon arriving at a foreign airport, try to get some local change before you leave the airport by making a small purchase, so if you're delayed on your trip into town, you will have the needed change to use a public bathroom, which many of them do require.
I pack half of my stuff and half of my husband's stuff in each of two suitcases. If one suitcase is not delivered, each of us still has complete outfits for the days until the suitcase is found.
Take a folding fan in your carry-on bag to use when the plane heats up and the air conditioning is minimal or nonexistent.
Make sure you remove those destination claim check receipts on your luggage upon arrival. Often they are not removed, resulting in misdirected luggage. If you check in with those tags still attached, don't be surprised if your suitcases are incorrectly routed. Best bet is to eliminate any potential mishaps by pulling them off once your luggage is back in your possession.
Playa del Rey