As a kid, my parents hid them in the deep recesses of their closet. When my kids were younger, we did the same thing - hidden in the closet. As they got older and wiser, we had to create more inventive places to hide Christmas gifts like a bag of old clothes or in the freezer. I've heard some folks use their car or keep the gifts at a friend's house.
Hiding things in plain sight always works best. We actually sealed some gifts in plastic and placed them in the trash can, underneath the liner. I also use a mail box (UPS Store) - they kindly keep my deliveries until I pick them up.