After the trip if you can print the pictures you took earlier, print them and collect them in an album or a letter (to remember later)
Try their food in a local restaurant not an extravagant one
Complement someone about their clothes or style (for sociable persons only)
Ask the people who work at the place about something in it ( like how this was built, is this lake salty or safe to drink). (Only for extrovert people)
Capture everything with camera or phone
Buy a souvenir if you can
Pick something from that place like water,sand or even rocks, literally anything that reminds you of that place, you can fill a little jar with water from that place.
