Their 5 considerations:

• Design for immediate access
• Keep gestures smart and simple
• Leverage clear mental models
• Design for real hand sizes
• Touch feedback is key

Usable: When you have a product that has a use, it needs to be easy to use. This means that is has to be intuitive. The person using it, shouldn’t have to think how he/she has to utilize it to fulfill his/her need. But this is not enough.

Desirable: It’s also a good thing that the person who’s going to use your product, actually wants to use it, not just because he/she has to. This can be done by use of a nice looking design and by making it fun and easy to use. For this, you need to tap into the emotional aspects of your product. (Also think outside the visual aspect, like the brand that might bring a certain prestige with it.)

Findable: When you have the best, most beautify and most usable product that ever existed, when no-one can find it. It might not even exist at all. People need to be able to find your product, but also find things inside your product (in case of a website, have a good navigation model and/or a search function).

Accessible: Your product should be accessible. This means for people with disabilities (about 10% of the population) but also from different devices (like mobile phones). This isn’t only good business sense (since you have an even larger target audience), but also because such requirements will become law in the future.

Credible: In order for a person to want to use your product, it has to be credible. So make sure that when it has an interface, it looks good (which style you use can depend on many things, from brand to personal preference). But there should also be information available about legal matters, security, privacy protection (when information is gathered),…

Valuable: It isn’t all about the people who will be using your product. In return it also has to deliver a certain value to you or your company, this can be in a monetary manner or in the form of customer satisfaction and reputation.

Finally, in the real world it is very difficult to have all of these points perfect. But it’s better to address each one of them and have a good result, than only address one and make that one perfect.

[From: Ambient Findability (book)]
[From: Semantic Studios]

• Users aren’t stupid. The system or application you designed just isn’t easy enough to use. This means that you need less complexity (preforable without losing functionality), simpler layout and better explain the user how to use it.
• Users aren’t lazy. Only very few users want to master the application they are using. Most of them just want to get their things done. So don’t expect them to know the system in and out. When they need an option that’s hidden away, why not point them in the right direction with some friendly text or a link?
• Users aren’t incompetent. As said before, most users aren’t technically experienced, so why not use ordinary understandable language? Words and phrases everyone can understand. The amount of errors that occurs (and frustrations that occur because of those errors) will also shrink when the user understands better what you expect from them. Why not even give them a hint? For example the format you expect a date to be in.
• Users aren’t perfect. There will always be errors that occur, maybe due to user input, maybe not. It’s the task of the developer to handle them and handle them nicely. Don’t be ashamed that something goes wrong and hide it. Tell the user if an error occured, why it happens and how it can be prevented (or when it will be fixed in case of a system being down for example).

So by keeping these 4 truths about users in mind, you’ll develop better software.