One could write books on this subject (and people have done so). Of course what is good for one person may not be seen as such by someone else. This is particularly so when designing UIs to be used by people with little or no familiarity with the digital world.
One of the problems is that a good UI is also a moving target.
I used to advocate Windows applications as being easy to use if you just followed the simple rules:
1) Tell the computer what you “thing” you want to do something to, by selecting it (often a single click with the mouse or a click and drag).
2) Right click and pick what you want to do with the pop up menu.
This scheme used to work with all good Windows applications. Sadly this uniform approach has gone and users (particularly those in the “addicted to mobiles” category) seem to be happy with the chaotic “every application has it’s own way” approach.
Thinking and planning the basic approach to your UI design must be sensible. I find that David Millington’s three postings about this subject are a good succinct set of documents to read and consider before starting a new project.
David Millington’s Good UI Design – part 1
Roger Cigol - Programming 