There are several aspects of UI/UX Design that work jointly to create an easy to navigate, satisfying experience for the user. These principles consist of Usability, Responsiveness, Consistency, Simplicity, Flexibility, Accessibility and Visual Design.

Usability: Usability refers to the ease of navigation and how comprehensible the layout of a website is, the controls should feel familiar and intuitive, your website should not be confusing to use.

Responsiveness: Your website should be as responsive as possible, Lag kills the user experience, You could have an otherwise perfect website that takes too long to load, and the load times would overshadow everything else. You should always be looking for ways to optimize your projects.

Consistency: Consistency ties into usability, if you use the same layout, colors and navigation elements on every page, the user will be able to predict how to navigate and have an easier time understanding your design, resulting in a more enjoyable user experience.

Simplicity: Simplicity is exactly what it sounds like, keep your website simple, if you add a plethora of unnecessary features it will increase the likelihood that your user becomes frustrated or overwhelmed by your design. Minimalist designs that allow the user to focus on the task at hand are best.

Flexibility: You want your interface to be usable on any screen size or orientation, by focusing on flexibility while designing you will end up with a product that's adaptable and scalable.

Accessibility: Your website should be accessible to the vast majority by including things such as semantic HTML tags, High contrast color palettes and appropriate text sizes and text spacing. Some more things you can do include closed captions for video content, as well as TTS for the visually impaired.

Visual Design: Your design should be visually appealing as well as engaging, Use bold, eye catching colors to draw the users attention to important information as well as an effective use of color and typography to communicate a hierarchy of options.

Source: https://dev.to/mohsenkamrani/7-crucial-ui-and-ux-principals-to-follow-2c63