At least two pairs of shoes should be on your feet at all times. Two pairs are needed for daily walking in the city and two for vacation.
A good idea is to make sure that you have enough clothes in both cases. If you are traveling by plane, you need to make sure you have an extra shirt, pants, underwear, and socks.
If you're planning on staying somewhere longer, you might want to think about bringing along a few changes of clothing. This will make it easier to go shopping for new outfits and won't make you feel uncomfortable.
Comfortable shoes are essential for those who take the bus or train. For those who drive, it is a good idea to have spare tires.
You should also pack lots of toiletries including shampoo, toothpaste as well as moisturizer and deodorant.
Finally, don't forget a flashlight, insect repellents, sunscreen, sunglasses, a hat and a first-aid kit.
You can put all of these items into one bag, rather than trying to stuff them in several bags. This will save you time and space.
Last but not least, make sure to bring a small towel & washcloth. You'll be able to use them when you take a shower after a long day.