Try these packing tips...

Losen all compression straps and draw cords on the pack and sit it upright on the ground before you start. Ensure that everything that needs to stay dry is in a plastic bag. Options include lining the entire pack sack with a plastic pack liner or rubbish bag, or individually protecting items in smaller bags. If you are spending time in very wet places, using a pack liner AND smaller bags is a good idea.

Seek to eliminate all dead airspace from the backpack. Air spaces are typically found hiding around bulky objects like stuff sacks and sleeping bags, inside pots/billies and in corners of the pack sack. Clothing will often pack better lose than it will in a stuff sack (however stuff sacks are useful for organsing items in the pack, it helps if you don't cram the stuff sacks to capacity). Tents will also sometimes pack better lose than in their sack (experiment at home to see).

RAM, CRAM and JAM! Really get the load tight and snug from the very first item (it is much easier to compress as you go than it is to compress the pack's contents once it is full). The finished pack should look even and symetrical, with no bulges, lumps and hollows. It might take more than one attempt to get it right the first few times you try this! Be patient.

Keep the pack's centre of gravity high and close to your back (between the shoulder plades). This will make a fantastic difference to the balance of the pack when you are walking. Make sure it is balanced side to side too!