Don Norman - the design of everyday things, focus on human centred design. Norman doors, human centred designs should have discoverability and feedback, designs should allow the user to discover their functions easily, there should be clear feedback for the user to understand if a design has been used correctly and effectively to complete its purpose.
A key element to consider when making designs is making sure that everyone can use them effectively regardless of ability, background and environment.
understand the user and their needs, reasons, and goals for using the website/app.
contextual inquiry - watch people and their process to learn points of issue, dont just rely on what they say, they are not designers they only know what they are familiar with and could request more designs that don't work for them effectively.
5 whys, the idea that not every problem exists on its own if there is one problem in a design there are probably several, by only fixing one of the problems it could effect the whole design. You should keep asking why things arent working until you find the core of the problem.
You need to find the root cause of the problem instead of just trying to fix the first problem that you find. By finding the root cause you more effectively and efficiently solve the problems prevalent in the design. not every problem exists on its own.
design and aesthetics is important but functionality is main priority - designs need to meet users needs - test using prototypes allow them to perform tasks and watch how it works. usability testing.
Empathize - research the audience, understand their needs for the design
define - define the problems discovered, layout clear problems that need to be solved