I have taken the time to connect an OTG (On The Go) cable into my Nexus 7 tablet to demonstrate for you how to take advantage of the USB Host capabilities of the device.  You can plug in USB input devices such as a keyboard or a mouse, or both, with the use of a USB hub.  You can also plug in a USB drive for extended data storage, as long as you download a free app from the Play Store called StickMount.  Now, StickMount requires that your device is rooted, so if you have not done that yet, please follow my "Idiots Guide to Unlocking & Rooting your Nexus 7" located HERE.

***edited by admin***