IOIO-OTG Hookup Guide
Joel_E_B, Ytai 
Troubleshooting
Driver Installation
If your IOIO is not showing up as a serial port, make sure you have installed the drivers from the Software Installation section. Going through the installation process again may solve any issues you may have with your PC communicating with the IOIO-OTG.
Updating Java
Some users may have computers running an outdated version of Java. If you encounter issues, please consider updating to the latest version.
To check which version of Java you are running, run this command in the Command line:
java -version
Download latest version here. Accept the License Agreement, and download the version that matches your OS.
JDK vs JRE
Using on an older MacBook to develop with the IOIO, I found that my Java version was outdated. When just the JRE was installed, it still did not update the version of Java pointed to by my Terminal. I found this Stack Overflow post about the same issue. Downloading the entire JDK solved my issue. However, if you do not wish to download the entire JDK, you can visit that post to see how to tell your Command line which version of Java to use.
USB Debugging
If you are having issues with your Android device not communicating with your IOIO, check the USB Debugging.
Ensure that USB Debugging is ENABLED (checked) when you have your Android device plugged into a computer.
Ensure that USB Debugging is DISABLED (not checked) when you have your IOIO plugged into your Android Device.
Check USB Connections
If the IOIO or your Android device is not communicating with the computer, check the micro USB connections. It's easy to plug one end of the cable most of the way in, but not quite enough.
Visit the Wiki
There is a plethora of information on IOIO's GitHub wiki. Visit there for more troubleshooting suggestions.
Contact SparkFun's Technical Support
If you have any tutorial feedback, please visit the Comments or contact our technical support team at TechSupport@sparkfun.com.