A few garment bags are considered carry-on size but more and more frequently they're getting checked at the gate. It is wise to avoid them if you possibly can.

If you're taking a laptop, to avoid attracting the attention of thieves, consider putting it inside a backpack or another unassuming bag. Use a sturdy bag that isn't see-thru.

Regardless of what type of bag you bring, there are a few things you need to do to each piece of luggage:

Put a lock on your bags. This prevents the suitcase from opening accidentally or otherwise. Keep the keys in your carry-on bag. 

To avoid confusing the baggage handlers, remove old baggage claim stickers or tags from the handle. You don't want your luggage reliving past glories without you. 

Make large, obvious and unique identifying marks on your luggage, such as writing your initials with White Out. Be sure to place your name, address and telephone number both inside the bag and outside the bag on a securely fastened tag.

Include a copy of your itinerary in each piece of checked luggage. Be sure your itinerary includes your home address and phone number and the addresses and phone numbers of the places you'll be visiting. That way, if you get separated, like Lassie, your luggage can find you.