In the Store: Fit comes first. Have your torso measured by a knowledgeable sales clerk who can help size and fit a pack. » As a general rule, the load-lifter straps should rise at about a 45-degree angle from your shoulders. » As an absolute rule, the hipbelt should wrap your hipsand stay there. Make sure to cinch it tight enough. » Raid the store's racks for ballast. Now load up and walk around. » Remember, it's easier to compress than expand, so choose a pack that's appropriate for the longest trips you expect.
In the Field: Pack symmetrically; a balanced load is more stable and comfortable. » Pack heavy items in the middle, close to your back, and stash layers and snacks where they're easy to get. » Long, hot day ahead? Store your hydration reservoir in the lid instead of the internal sleeve and you'll be able to refill without unpacking. » Storm coming? Instead of using a rain cover, store your gear in waterproof stuffsacks inside your pack.
At Home: Clean your pack with mild soap and water and it will last longer. » Dry it thoroughly before storing.