Know your requirements:
First of all, you should know your requirements as this can really help you to buy a suitable backpack. If you are not interested to keep your gear inside the bag or you want to have more sections to enjoy easy loading and unloading then an external-frame backpack is the ideal choice. They are simple in design, easy to pack and carry but a little bit heavier than regular bags.
Decide your budget:
Knowing your budget is very important as backpacks come in different varieties and prices. You may have to spend from $75 to $300 for a good external-frame bag. Just check how much money you can spare for backpack and then start looking while staying within budget.
Look for comfort and ease:
You must make the comfort and easiness of wearing your first priority as most of the external backpacks become heavy because of the metal frame. You should pick a bag that has curved shoulder pads, an adjustable suspension system and contoured frame. Moreover, you should buy a bag that can carry all your stuff easily. As there will be lot of hiking involved in the trip so make sure you can carry that bag with minimum effort.
Pick a waterproof bag:
As there is always a possibility of rain in the summer and snow in winter so it is better to buy a bag with a water resistant shield. Mostly, the manufacturing companies make bags with a zipper which becomes beneficial in case of any unexpected weather condition.
Check the durability:
You should not try to save money and buy a low quality backpack. The wise approach is to buy a durable bag by spending a few extra bucks. Check the stitching, zipper, straps and the strength of the fabric that is used. Remember to take your time and look at all the features to help you decide on which one to buy.