The issue of luggage comes up today--as I find out size does matter when it comes to luggage.
1. Carry good bags. Cheap luggage at WalMart--doesn't go far.I was guilty of purchasing this massive inexpensive suitcase at WalMart- only to have the handles tear off of the side on my first trip, on the way home. It is best to purchase quality luggage rather than cheaply made--that'll fall apart at the airport. You know how those baggage handlers throw your stuff around. Stick with quality.
2. Size does matter. Though some airlines differ-the guidelines for carry-on baggage are 45 linear inches, as it must fit into the overhead compartment. Also not more than 40 pounds. A good idea would be to purchase luggage that "fits" the FA-A's (Federal Aviation Administration) standards. Also avoid overloading--cause you'll literally pay for it at the airport. The US webite is www.faa.gov
3. Pack smart. There are various good books out there on packing your bags efficiently. Remember to keep all your vitals like glasses, medications, colognes and perfumes, emergency numbers and such in your carry on. Nobody wants to open their luggage and find that cologne bottle to be shattered--dowsing everything. A good book on packing smart would be "The Packing Book", secrets of the carry-on traveler, by Judith Gilford.