With the diverse range of rucksacks available it can seem a confusing choice to the uninitiated, but the main factors you should consider are actually quite simple.
Capacity of the bag - How long is your trip and how much do you need to take?
What size you are - Your height and build will determine the size of the pack.
Backpacks are measured by the total capacity of all of the pockets in litres. For a one day trip a 30 litre pack will accommodate your clothing, water, accessories and food. For three day hike a pack which is 50 litres will be more than sufficient for your clothing, tent and sleeping bag. For a trip of 1 week and over, you should look for a sack which is 70 litres, with the ability to expand by 10 litres, (especially useful for presents to take home).
Pack the Right Kit
Your key consideration is that on any trip you will have to carry what you pack! Although that sounds simple enough, the principle of packing the right kit and not much of it, is a good one to follow.
Once you have selected the size of the bag you then need to consider the way in which it fits on your back. Different packs are designed to fit people with longer and shorter backs, and Mountain Warehouse stocks all types.
70 percent of the weight of the sack will sit on your hips, so you must make sure that a pack has a padded hip belt and that when adjusted it sits on your hips, not around your waist. When selecting your pack online make sure to select a back size that is appropriate to your frame, or select one which is adjustable. If it sits too low then the bag is too big for you - especially applicable for the female readers among you, and vice versa for the great and tall among you.
The heart of a great rucksack is in the back system. With a smaller sack there is a variety of padded and ventilated backs to keep your back comfortable and dry. Larger rucksacks have internal frames to distribute the weight of the bag and support it on your hips.
Other features which are you may find useful are a split main compartment - so that you can keep your packing organised, a rain cover to keep off light rain and compression bungees on the top or bottom to attach your tent or sleeping bag when you run out of room in the main pack!