Some people are into buying souvenirs and some aren't, so this one isn't for everyone. Do you like cheap tchotchkes from foreign countries? Can you not resist that handmade throw rug or silken muumuu? Is it impossible for you to not add to your shot glass collection? If you've answered yes to any of these questions, then do yourself a favor and pack an empty bag in your luggage to carry your purchases. Even if you aren't into this, you may need to buy some souvenirs for family and friends. Chances are your luggage and carry-on bags are already maxed out, so if you have an empty bag you can buy to your heart's content. Pick a bag that you can fold up in your suitcase that won't take up too much room. How large of a bag you need is your call. If you aren't into buying things on vacation, skip it all together. If you have a shopping addiction, bring an appropriately-sized bag.