My wife and I are relatively new International Travelers and we credit
Rick Steves as being the primary reason our travels have been so enjoyable and trouble-free.
While Rick has focused primarily on Europe during the past thirty years he is branching-out to other parts of the globe. His Web site and podcasts of his radio show are chock-full of good info; his podcast can be found at the iTunes Store. And the forum at his Web site is an excellent source of first-hand advice from fellow travelers.
I think that Rick's travel primer "Europe Through The Back Door" is Essential Reading when heading to Europe. It isn't a guidebook in the usual sense: it is a "how to travel" guide that has saved us time and money.
To echo Dick's post: travel as lightly as possible. My wife and I take one carry-on bag and one daypack each. We have traveled for up to a month at a time out of our bags and we haven't missed a thing by carrying less instead of more. You would be surprised how many "essentials" we can stuff into our bags and still avoid checking luggage, dealing with multiple/large bags getting in and out of taxis/public transportation, traversing busy city streets and carrying our stuff up flights of stairs in buildings lacking a "lift." (FYI I am 54 and my wife is 61...)
After years of trial and error we settled on an earlier version of the
Eagle Creek Switchback Max 22. Yes, it is pricey but we're talking top-quality here, something that is meant to take a real beating... A couple of years ago a Seattle hotel door man even commented about the quality of our bags and you can be sure that he handles a LOT of different bags in his job! Being able to choose between wheels and a very sturdy handle and hidden backpack straps is a real plus when your travels take you through crowded airport terminals and cobblestone streets.
When the daypack is detached from the main bag you meet the standard carry-on requirements. I choose to use
another daypack because I need something somewhat larger to carry my camera gear and small
Baggallini Messenger Bag that I use for day-tripping. My daypack also has a first-rate suspension system for carrying heavier loads; I slip it over the bag handle and it rides on top when I am "wheeling" my carry-on bag. My wife takes along a very small fabric purse that fits inside her daypack. She also favors a couple of very stuffable shopping bags that are available on the Rick Steves Web site.