On my first trip abroad I bought an inexpensive, external-framed pack.
Not only did I discover that it wasn't quite waterproof, but after several months of being battered on luggage carrousels and jammed into overhead luggage racks, the frame started to part.
And because I hadn't added any highly visible identification, I almost left an airport with someone else's pack.
I believe it's best to use a backpack when traveling independently. Then hands are free to hold guidebooks or maps, and because the weight is carried closer to a center of gravity, there is less stress on shoulders.
When you shop for a pack, don't cut too many corners to save a few dollars. Some common problems with budget bags are that they can be water-resistant rather than waterproof, the seams might not be double-stitched and edges of the material could fray.
Sometimes inexpensive packs are also made with thread that deteriorates after being damp several times.
If you are going to buy a pack, here's how to get started: Decide if you want an external or internal frame. The external frame is good for carrying loads of 100 pounds or more and a cross-strap keeps the pack from lying directly against your back, a relief in very warm climates.
Damage Comes Easy
The problem with this type of pack is that it's not easy to store in luggage compartments and it's easy for the frame to be damaged when it's tossed around.
Advantages of the internal-frame pack are easier storage, less parts to catch when sent through luggage services and they can convert to look like sporty suitcases for the times when you don't want to appear to be traveling quite so casually.
Also, decide whether you want a top-loading or front-loading pack. If you choose a top loader, items can be taken out by a friend without you having to take off the pack.
You can also load more because of an adjustable top flap that simply ties down.
The advantage of a front-loading pack is that they usually close with a zipper and you usually can lock them.
Where to Buy
In addition, it's important to buy from a store that specializes in such equipment. More likely you'll find a sales staff that is knowledgeable in various models and will load a pack with weights and adjust the frame so that you can decide on the most comfortable fit.
Make sure your pack has a hip-belt. This distributes the weight onto your hips and reduces stress on your shoulders.
If you choose a pack with side pockets, although they are handy for carrying items such as maps and guidebooks, it is possible for a thief to reach in without you noticing when you are bumped in a crowd. Don't keep valuables in such pockets; keep them in a pouch under your clothing.
Add a badge or a crest to your pack to identify it at a glance. Two similar packs could be unloaded from the same plane at the same time. You could pick up the wrong one or someone could mistakenly take yours.
When you load your pack, it will be more comfortable to carry if you keep the weight high, but below the shoulders. Lower the weight for improved balance if you are walking over rugged ground.