How do I go about creating an Icon set for Ubuntu? The basics at least.
Ubuntu uses the Gnome Human Interface Guidelines (number 9 ) you can follow these to make your Icons fit for the Gnome Desktop. Ubuntu also has guidelines for the Indicators as noted here.
Create them using whichever software you prefer, they need to be in .PNG or .SVG
Look at the folder structure of any icon set so you know how you should organize them for them to work. And so you also know what are the names of the icons.
Unity doesn't specifically use a theme it takes on the System Theme.
And lastly use your creativity.