There are a few basic steps that you must follow while packing.
Making a list of all the essentials needed is something you should start with.
Secondly, you should weigh all the items that will go in your backpack. Once you do that you will have a clear idea about what can be left behind to make the backpack lighter in case that needs to be done.
Use multifunction gear as much as you can. This reduces the number of items that you need to carry. Thus reducing the clutter in the bag and making it lighter.
Here are a few pointers to help you understand the above-mentioned points more clearly.
The three things which make up the major weight of the backpack are the sleeping bag, sleeping pad, and the tent.
Carry a lightweight sleeping bag and down blanket instead of a sleeping pad. This will significantly reduce the weight of the backpack. The down blanket you carry can double up as a jacket or vice versa.
Carrying a lightweight tent is also very important. Trekking poles can be used as multipurpose gear as they can be used to hold the tent. It eliminates the need for tent poles. If you are going for a trek where you might not need a trekking pole, you can use rocks to anchor the tent to the ground.
If you are able to reduce the weight of the sleeping bag, sleeping pad and the tent it will help cut down a remarkable amount of weight. As a result, you will be able to use a lighter backpack of lower volume.