UI design plays a fundamental role in the overall quality of your end product. The UI not only supports the UX work, it expands on it by bringing together concepts from interaction design, visual design, and information architecture. The results of a good UX and UI rely on knowing your users. Getting to know their goals, needs, preferences and tendencies. However, there are a couple of UI design principles that might help you improve the UI of your website or app.
Reduce visual clutter: This is one of the biggest issues in some interfaces. The whole point of removing clutter is to reduce the noise in the page so the most relevant pieces of information can surface and get the appropriate attention. Removing visual clutter will help your users complete their journey through your interface efficiently.
Consistency: Keeping consistency across an interface is not an easy task, there are many elements with countless variations. Designing interfaces has shifted from a very manual process (creating individual pages) to a more systematic one by designing with components. Components are the pieces of the puzzle that will come together to form the interface. This is when a design system comes in. A design system is mainly formed by a pattern library (where your components live) and a style guide. By having all your components and styles in one place you will be one step closer to having a consistent website or app.