This is a growing list, but for now it's about simplicity, minimalism, consistency, easy use, navigation, user experience, colour code.

  1. Simplicity.Simplicity is not the opposite of complexity, it's complexity put well. If you cut out the complexity, you cut out the value. Who would buy a washing machine with two buttons on it offering ‘Wash’ and ‘Dry’ only? Hardly anyone because it looks dumb. Digital products are no different, they need to showcase their capacity and their smartness right at the beginning, and they need to do it in a well-organized way. Their complexity carries their value.
  1. Minimalism. Contrary to popular belief, minimalism is not about cutting out everything from the interface until a single line is left. Minimalism is replacing everything on the interface with one brilliant idea that gives a brand new meaning to that single line left. Brilliant ideas are hard to come by and are often hard to notice, they just make things work smoothly. If you see an interface that come across as being empty rather than smart, then it probably is empty.
  1. Consistency. By definition, consistency occurs when the cause-effect link is obvious. For example, clicking on a menu item opens up a new page with a certain page load in the case of every menu item. That is consistent behaviour. How consistency as a term is used out there is mostly in terms of ‘similarity’, e.g., putting every button on left side regardless of their function and relation to the page content. Also quite often used as ‘copying’, e.g., repeating the same layout page after page, regardless of the nature of the information displayed. Sadly, in the hand of a less-experienced designer, consistency – under it false guise of copying – becomes an ultimate explanation for repeating the exact same UI solutions mindlessly on every page.
  2. Easy use – no more than three clicks. A tool is easy-to-use tool when it doesn’t require more cognitive effort than the users were intended to invest in their task. The myth of the number of the clicks has a long history of being misused or, more likely, used in a misinformed way. Generally speaking, if it’s not clear what needs to be clicked and what the consequence of that click is, that makes it an expensive click that requires cognitive effort from the users. As such, it burns down the cognitive resources that were allocated for the task much faster. Visitors tolerate these kinds of ‘expensive clicks’ much less than the intuitive ones; hence, the number of these kind of clicks must be reduced when laying out the click-flow. We can also say that the often-used paths/flows need to be designed with low click numbers, while the rarely used paths/flows can incorporate up to dozens of clicks. Tip: instead of squeezing every step into one page to reduce the number clicks, consider wrapping the functionalities based on their relation and revealing them on demand.
  1. Navigation. Navigation is not a synonym for the main menu (also known as top menu), as is often assumed. Instead, navigation includes the in-page click-flows, (leading from button to button) and the contextual menus/options, as well. Navigation describes one’s effort to find one’s way from a current location to the target location. Doing so requires two things only: knowing where one is at all times (making one’s position clear in the page hierarchy) and knowing where one wants to go. This definition makes it clear immediately that breadcrumbs are much more important than the top navigation and that repeating the page links like crazy won’t help the visitors figure out where they want to be; while the context will. In fact, visitors only use the top menu when the in-page click-flow fails and they need to go back to a basic page (re-anchoring themselves) to start again.
  1. User experience (UX). A user’s experience spans from anticipation (previous knowledge about the product) via action (connecting to the interface) to recounting (looking back and summarizing). In other words, it starts with what visitors hear or read about the product and ends when they themselves talk about it to others. Accordingly, the usability of the product, which is often incorrectly used as a synonym for UX, is only a small part of the entire experience.  An even smaller part of UX is where to put a button; yet, the most common sentence I hear is: ‘We shouldn’t put that button there because it's bad for UX’.
  1. Colour code. When colour-coding on the UI, we use colours as a grouping tool to make certain elements appear to belong together (align with the Gestalt low of connectedness). Simply colouring the icons and boxes is not colour coding, it is what it sounds like, colouring. Colour coding  is used mainly to support user navigation (in terms of navigating their way through the platform). Accordingly, when it is not used consistently, it loses its function and falls back to become mere colouring. How a colour code is put together depends on the number and type of the interactions we wish to distinguish. We also need to consider the erroneous human colour memory, the limited working memory sources (short term memory), conventions and cultural differences. As a consequence, when creating colour code systems with the above in mind, hardly anything is left to guesswork or personal preferences.