Use vacuum bags the right way
First, make sure everything you want to store is clean and completely dry. If you store anything that is even slightly damp, you run the risk of getting mold and ruining your clothes, quilts and the like.
In addition, make sure you have the right size bag for the amount you are storing.
Open the bag on a flat surface and unzip the zipper. Fold the materials and carefully place them in the bag. You can stack the items on top of each other, but make sure the bag is not too full. Make sure there is a few inches of space between the edges of the clothing and the closure. This is because when you get the air out, those extra inches of space will stick together and improve the vacuum, minimizing the amount of air that leaks in.
With the clothing in place, use the plastic clip to zipper up the plastic zipper. Go over the zipper again to make sure it is completely closed.
When you are finished, loosen the valve cover by unscrewing it, then place the vacuum nozzle without attachments over the cover. Simply press it against the valve, and then turn on the vacuum cleaner. Continue to press it firmly and the air will be sucked up.
While removing the air, be sure to press the portions of the vacuum bag that are away from the valve firmly, otherwise the end result will be very lopsided and uneven, making it more difficult to store. Afterwards, if you feel that the clothes in it are too close to the zipper, open the bag and move it. Since you just took the air out, the contents will naturally fit a little better even if you open the bags again, since they are not fully inflated again until you shake them up. Then close the bag again, making sure it is perfectly sealed, and use the vacuum cleaner to get the air out again. When you are done, screw the valve cap back on tightly. The self-closing valve won't let air through while you're doing this, so there's no need to rush when you turn the vacuum cleaner off.
To open the bag, just pull open the zipper. Do not let the air in through the valve.