Walking into a camping store and seeing a wall full of packs can be daunting. Which one suits the needs of you or your camper? What is a good price? Should I buy a youth-sized pack? Where is the frame?
First you should determine the you or your camper's size. Many camping stores will have pack sizers that look like the picture below. The lines at the top of the yellow piece determine the length between the hips and the shoulders. The white pieces go around the waist to determine the size of the hip belt.
Most modern packs are widely adjustable. A good example of this is the EMS Long Trail 70. Available online and in all Eastern Mountain Sports retailers, the Long Trail 70 is a comparatively affordable option. At $189, the Long Trail has fully adjustable shoulder and hip components and can be made to fit a hiker with 15" between his/her hips and shoulders (approximately 5' tall).
The Long Trail is a top-load pack with the majority of its 70 liter capacity in one large portion. A second, smaller compartment closes over the top of the main body of the pack. The small top compartment clips into a set of adjustable straps that allow to tighten the load against the body. This is a common feature in top-load packs and the Long Trail performs adequately in this regard. Below is the shoulder adjustment. This area of the pack rests near the top of the hiker's back. The shoulder straps can be removed and reattached up or down to allow for a taller or shorter hiker. The Long Trail does this easily and effectively.
The Long Trail has a large and well-padded hip belt. A nice feature about he Long Trail is the doubly-adjustable buckle and straps. Rather than just one loop through the buckles, the straps loops through a second plastic locking piece. This protects against the belt from wiggling loose while hiking. It prevents added pressure on the shoulders and repeated stopping to fix the hip belt.
The bottom of the Long Trail has a zipper that provides access from the outside of the pack. Inside the bottom of the main compartment is a flap with a zipper that allows for a smaller compartment to be created. This is a nice feature that lets the hiker keep an item -- food, the first aid kit, a sleeping bag --separate an easily accessible.
All over the Long Trail are many clips and straps that let the hiker tighten the load closer to the body. These compression straps, such as the one pictured below, are an important and sometimes overlooked feature. They make for a much more comfortable and efficient hiking experience as the contents of the bag jostle less.
Other features of the Long Trail are straps on the bottom for a sleeping bad, a compartment for a hydration bladder, and mesh pockets for a water bottles. The Long Trail is a nice, versatile pack for a young hiker looking for a first pack or looking to upgrade to something with more space.