Getting a development version of ubuntu installed is the first step to being able to provide test results for ubuntu.
Setting up the installation
If you are new to testing, try using testdrive to get a development install up and running. It will setup a virtual machine with the latest development image of your choice which you can then install. Once installed you can use the virtualbox virtual machine as your test installation.
Obtaining an image
Daily images of ubuntu development are available on the cdimage server. You want to grab an image from the current builds. Download the image of your choice.
Once you have an image you can install it into a virtual machine, such as virtualbox, or onto physical hardware. Feel free to use a cd, dvd, or usb drive as a medium to install on physical hardware.
After installation, you can keep your install updated the same as a typical ubuntu installation. Use the update manager to update as new packages arrive. Alternatively utilize the command line via sudo apt-get update && sudo apt-get dist-upgrade.
Be very careful that your upgrade is not holding back or removing essential packages. If you encounter an upgrade that looks suspect, it's best to wait and try again at a later time. The archive state in general should be kept clean, but a partial upgrade is possible.