Snap a picture of any bags you intend to check with the airlines. Hopefully you won't be one of the many whose bags get misplaced by the airline, but if so it helps if you have a photo of the bag(s) to show them what they should be looking for. This worked for me recently when my bag didn't appear on the caroussel, and when I showed the attendant the photo of my bag with the blue handle, she remembered taking it to lost and found. I had my bag in a few minutes due to that photo.
Snap a photo of anything out of the ordinary you pack in checked bags. I have a system where I pack all of the power bricks for my mobile gear in a cable stash. I put this in my checked bag to keep my backpack as light as possible. In the event the bag is lost and a claim needs to be filed, having the photo of the cable stash shows all of the expensive power adapters in one shot. Hopefully you won't need to replace gear due to a lost bag, but if so make the process easier.
Snap your car in the airport lot to remember where you parked. Even worse than forgetting your hotel room number is forgetting exactly where you parked in the airpot lot. The end of a trip when you are tired and anxious to get back home is not the time to be wandering aimlessly in the vast parking lot trying to find your car. Take a couple of photos with your smartphone camera that clearly mark where you parked your car. This can turn a bad travel day into a good one in just a few seconds.
Take a photo of your hotel to show taxi drivers. If traveling abroad where English is not the native language, communicating with taxi drivers can be a chore. The easiest way to communicate where you are staying is often to show them a picture of the hotel. You'll be back in your room in no time once they realize where you want to go. Hopefully you'll remember your room number when you get there.
Image credits: Flickr user BrentDPayne ; Hunter-Desportes