There are several things that can help new users to get started.
First, consider starting the new users on a web-based solution that doesn’t require any installation of software. Often such a solution will give them access to a lot of the standard functionality they need.
After some time, they might need to move on to a more powerful desktop GIS. For the desktop GIS, the interface needs to be easy to use. It would also be helpful if they in some way are able to easy costumise it to their needs and be able to group the features and functions they use.
We have found that giving them access to a search feature directly in the interface makes it easier for users to learn a new interface.