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Before you fill up your backpack and start wearing it, you will want to properly adjust your backpack.  Adjusting your backpack can help make it more comfortable and help prevent injury.  Make sure your backpack fits properly before you start regularly using it.  Most backpacks will have an area on the straps that you can use to adjust the length of the straps themselves. Pulling more or less strap through the buckle will adjust how long the straps are. Adjust the straps of the backpack until it fits snugly against your back. Avoid leaving too much slack in the straps of the backpack as wearing the backpack too low can hurt your back. Make sure both straps are an equal length to ensure that the weight of your backpack is evenly distributed. Once your backpack is correctly adjusted and customized, you can start to fill it up with whatever you need to carry.  Be careful when packing your bag to prevent fragile items from being broken.  Take some time to see how your items will best fit in your bag before putting it on to wear it.  Fragile items should go on top of more durable ones. Some items may have an usual shape or sharp corners.  Try to position these so that they don't poke you in the back. Make sure any containers storing liquids are secure before adding them to your bag. Don't carry more than 10%-15% of your body weight in your backpack to avoid injury. Now that your bag is full and adjusted, it's ready to wear.  Most backpacks will have two shoulder straps that will both need to be used.  Put an arm through each of the shoulder straps to make sure the weight is properly held by your backpack.  Take note of how comfortable the bag feels with items in it and make adjustments if needed.  Do not wear your backpack with only one shoulder strap. Each arm should go through a shoulder strap. Backpacks should not drop below the waist level. Don't wear your backpack slung low on your back.  You may need to adjust how you packed your items to evenly distribute the weight. Some backpacks will have an additional waist strap that can add more stability when worn. After you have found a great backpack, you can start to personalize it.  Personalizing your backpack can help keep it identifiable and allow you to express yourself at the same time.  Consider adding some contact information or other personal stylistic elements like patches, drawings, or tags to make your backpack feel like your own.  Writing your name and phone number on your bag can help it get back to you if lost. Customizing your bag can help you identify it easily if it's near similar bags.
Adjust your backpack. Fill up your backpack. Wear your backpack. Personalize your backpack.