Getting a backpack is quite a big deal in the whole travelling spectrum of your trip. Being as you will spending ALOT of time with it you have to be quite certain its the right one.
Luckily choosing the right backpack is not all that hard.
Side opening case.
The first thing I have found first hand is that a side opening back pack is essential ((basically so it unzips like a suit case), it may be you will pay a little bit more for this, but you will definitely be grateful for doing it. Top loading bags means you become an amateur forager… Sure digging through the to the bottom of you bag to get a T-shirt is fine when you start travelling… But 3 months in digging down to the bottom of the bag will come a tad relentless and the emptying everything out because you think you’ve lost something may get a tad annoying!
It may seem obvious but the bigger the bag the more stuff you are going to put in it. So you need to assess your travelling and what you ‘roughly’ be expecting to do. i.e… if you are staying in 1 country or will be going from hostel to hostel via coach or car a big bag 70-80ltr will be fine (annoying… but fine). If you plan to use public transport or going to be in confined spaces (i.e. boats etc) having a smaller bag will probably be better as banging up the aisle and sitting with a big 70ltr bag on your lap isn’t great! If you are going to be doing lots of walking with your bag, the smaller the better.
Most bags are fully adjustable, so your height and stature shouldn’t be a problem.
A few things to bare in mind… Your local travel shop will be more than happy to help you out and will do all the adjustments needed. BE SURE to get you bag adjusted.