Well, there are lots of things you may look for but see the things below matters most for a great backpack:
- Is there any rain cover?
- What about the water reservoir system?
- Is there any water bladder?
- What is the size of the water bladder?
- Does the bladder come with a magnetic tube?
- How many pockets are there in the bag?
- Are those pockets well enough for organizing my stuff?
- Are the sliders lockable?
- Is there any laptop pouch or can I take a laptop in it?
- How about the external attachments?
- Is the waist belt removable?
- Are there pockets in waist belt for quick stuff?
- Is the pack water-resistant?
- Is there any strong lifter?
- Is the daypack included?
- What is the size of the day pack?
- Are the zippers smooth and not covered for easy access?
So, these are the basic things you should look in a backpack for finding the great. Besides that, you may also have questions about fabric, material, etc.