PackHack: Roll up your clothes
The rolling of clothing has long since proved to be one of the most space-saving packing methods among travellers. In order to get some extra volume, it is also worth filling the cavity in shoes, e.g. with socks.
Another space-saving packing method is the proven Ziploc freezer bag packing method: Press all the air out of the bag after you’ve stowed your clothes in it. So you can make a few inches in a limited suitcase or backpack.