Playing games, trying to fumble in ignorance with the Internet (back when it was very basic), learning every crook and ridge of Windows.
Also play with Hot Wheels, disassemble everything I could find when I got to my father's toolbox, and making my little sister laugh.
I still play games, I am now extremely knowledgeable of the Internet, and I know Windows 98, XP, 7, 8.1 all throughout and have an advanced knowledge of Debian-based linux systems. To top it off, my sister and I laugh harder than ever now that SHE knows Internet.
No hotwheels, though, and screwdrivers only on my computer.