Designers of digital products and services; here is a thread of principles that I like to keep in mind...

Jakob's Law: Users prefer interfaces they already understand. Use a familiar design pattern. Don't reinvent the wheel.

Occam’s Razor: The simplest solution is usually the best. If there are lots of solutions that make different amounts of assumptions, the one with the fewest assumptions is best.

Pareto principle: 80% of the effects come from 20% of the causes. Hard to swallow but this means 80% of the increase in revenue/user growth/whatever KPI comes from your core 20% of features. This doesn't mean stop adding features, it means prioritise the experience of those.

Parkinson’s Law: Any amount of work will inflate to fill the available amount of time. Keep this in mind when managing teams and yourself. Set a deadline. Respect it.

Postel’s law: Be liberal in what you accept and conservative in what you send. In UI/UX this means take in multiple inputs of data but be precise and astute in the feedback you give the user. Do not confuse them with information they don't need to see.

Serial position effect: The first and last elements of a list are more likely to remembered. So put the least important things in the middle.

Von Restorff Effect: When similar elements are together the ones that differ are the most likely to be remembered. E.g. Trying to make a special accounts out? Don't put them all in one place, put them in the middle of the normal ones and make it a different colour.

Doherty principle: Computers and humans work best when neither has to wait on the other. Nobody likes waiting so when a user clicks a button let them see something happen immediately (preferably something should happen in <400ms)

Hick’s Law: Too many options makes it harder for a user to make a decision a.k.a choice paralysis. Limit the decisions a user has to make and how complex that decision is.