Packing a backpack is not rocket science but it does require some attention to details if you want to avoid minor frustrations like having to stop and dig something out of the bottom of the pack.
While there are some variable to consider like climate, duration of your trip, type of backpack you own and a few others, there are some basic principals for packing a backpack that you can adapt to practically any situation.
First, pack for comfort. One factor that greatly affects your level of comfort while backpacking is the weight distribution of your gear. Basically, you want the heavier gear in the middle of your pack. Also, make sure the total weight of the backpack is evenly distributed on each side.
Second, pack for accessibility. Make sure that the items you need more often are easier to get to. A good plan is to pack in layers starting on the bottom with your sleeping bag, followed by your tent, then your bedroll, cooking gear, toiletries, first aid kit and, finally, food.
Your clothes can be packed according to the need to balance the weight of your gear. If the heavy equipment is too far down, add some clothes underneath it, otherwise, place your clothes on top.
Besides the top of your pack, use the side pockets for things you need to grab quickly. Some of these items might include your rain gear, snacks, water bottles, insect repellent, maps, gloves, etc.
Another accessibility issue deals with gear that goes together. Pack items that are used for similar purposes near one another in your backpack.
Finally, pack for prevention. Pay special attention to the following tips so that you an avoid ruining your gear. Keep plastic and loose fabric away from zippers. If caught, you run the risk of damaging your gear, breaking the zipper or both.
Keep anything that has liquid contents upright and, if possible, in a hermetically closed bag. Any hazardous materials or products that could stain your clothes or destroy your food should be packed in outer compartments.
There are two final tips that make packing a backpack an easier task. One, begin early. Give yourself plenty of time. You are more likely to forget important items or pack badly if you are under pressure to get it done quickly.
The second tip is to make a list of all the items you want to pack in your backpack. Once completed, prioritize the items. Include essential gear at the beginning of the list and stuff you would like to take but are necessary towards the end.
When you start the packing, begin with item number one. Go down the list until your backpack is either full or reaches a weight that you are comfortable with.
Now you're ready to hit the trails.