You have already gotten lots of great advice but I'd say one of my big tips (beyond what's been offered) is to pack light. We always have a goal of not checking any luggage and it makes travel so much more fun/enjoyable to just have everything in a backpack. It also makes it much easier to get around your destination location on foot or via public transit, so you will avoid spending tons of money on taxis and have an easier time accessing things since you no longer need a decent sidewalk or elevators to haul your suitcase around.
Hey cats, I love your idea of traveling with backpacks instead of suitcases. Do you have any recommendations on which type or make of backpack is best? Do you use one backpack for all kinds of purposes (like flying, hiking, day to day) etc? Are they pricey or cheap? Any thoughts you or others have on best all around backpack for travel would be cool.
The best one is the one that fits the person who will be carrying it. I've had several backpacks for various travel purposes (flying, hiking, day, and travel/suitcase) over the last 15 years and the ones I've used and loved the most have been the ones I tried on, with weights, and had properly fitted in a shop. Every single one that I've bought online without trying it on and fitting it has ended up on ebay eventually. Get it fitted, ask them to put weight in it (if they don't have weights to put in or don't understand what you mean when you ask this, that may be a sign that this is not a great place to buy a backpack), and wear it around a while to see how it feels. If you have friends who can loan you some packs to try, that's ideal. I definitely didn't know what features I really really wanted in my hiking packs or even what sizes I needed until I was a few trips in.
I personally really love Osprey bags (their 15L Daylite is my favorite daypack) and I have their Porter 46 for a travel bag--I am getting to a point where I do a lot more with a rolling suitcase than a travel backpack but this bag is great for situations where I don't want a wheeled bag. It also fits me well, which is a personal thing and hard to know without trying it on. Be aware many good backpacks come in sizes based on torso length, so if you are buying online be sure you know what size you need.
I use my hiking packs as my laptop backpacks and flying backpacks. I have a 15L Osprey Daylite (also my city tourist bag and frequently used in lieu of a purse), a 22L Montane pack, and a 30L Gregory Jade pack, plus the 46L Osprey Porter. I don't do overnight hikes so these bags cover all of my day to day, hiking, travel, flying, laptop bag needs.
None of these were particularly cheap but they are all high quality, should last an extremely long time, fit my frame comfortably at the carrying weights I need, and have all of the features I wanted. I waited for sales and coupons for all of them--REI staff are usually really great at both fitting a pack for you AND telling you not to buy it til it goes on sale in 6 weeks. :)