Remember to get a variety of sizes in boxes. It is usually best to have more smaller to medium size boxes because those are easier to fill up. If the box is not filled to the top then it is not stackable. When you get larger boxes it is harder to fill those boxes to the top. In the instance that you do have more room in a box, it is best to fill that space with towels, curtains or other items that give it protection but also offer support so it can be stacked. Also, remember an important rule: the heavier the item, the smaller the box! It is easier to put heaver items in a smaller box because it is easier to carry. Having heavier items in larger boxes make it harder to carry. It is best to put lighter/awkward items in the bigger boxes to make them easier to carry.