With your fingers, locate the uppermost part of your hip bone. Your hips will form the foundations of how your rucksack sits on your body and support the majority of the pack’s weight.
Now, fill your rucksack with improvised weights, such as tinned food or bags of rice. This is to simulate a fully loaded rucksack, as this is when you'll need comfort the most. Take care to weigh the pack evenly and pad it out if necessary, then put on the weighted rucksack and allow it to hang freely from your shoulders.