Over the years I picked up a few things. I'm positive someone's stated it better and more complete before, but nonetheless these are... My Rules for Design.
They're not going to read everything you wrote.
They're not going to view anything in any specific order.
They're impatient, and easily bored or frustrated.
Start with the punchline, then elaborate and work your way back to it.
Increase scannability.
Everything is not "the most important". Make it faster to find pertinent content by building contrast in your information using purposeful segmentation into quick-to-understand chunks.
Get to the point.
Always look to present the shortest path to everything. Consider the number of steps from any section/page/screen to another.
Be fast and easily understood.
Don't be verbose. Reduce noise but present all contextually important information.
Encourage browsing.
Keep interactions simple and conducive to experimentation.
UI is a stylesheet – the elements of a design system. Iconography, fonts, colors, and styles...
UX is an exercise in prioritization toward a goal – how you'd use the UI to guide someone to do or learn something by organizing information and building a hierarchy of elements. "Look over here!", "Do this!" or "Here are your options:"
CX is content mapping – laying out the strategy for how a user should, but also might, navigate your content. It's about making sure information is clear and contextualized, and serve the greater goal of the user doing or learning something.
Label things appropriately.
Always make it clear what information can be found in a section if some or all of it is hidden (see dropdowns).
Don't scare with call-to-actions.
Encourage browsing! Don't make it seem like the user is committing to something or have to go somewhere else – unless they are or do. Use soft actions like "Learn", "Explore" or "Browse" that would imply that they could come back if they didn't find what they were looking for.
Carousels are usually bad.
Though flashy, carousels are by design hiding information and should only be used for featured content or non-critical lazy browsing.