Take your design out of Graffle, Visio, Axure, Photoshop, InDesign or whatever, and get it off the computer. Whether you use specific prototype tools, printouts or just put screens into the device gallery, get it onto the device or somehow check at device scale. 

Start your UI design at scale. There are many templates you can print that allow you to sketch at the scale of your device, or many devices. 

Check your work in real environments. Even before actually testing with users, simply trying the design on the actual device outdoors, walking around, in loud places and however you think your users work will help a lot. Things look different on the projector, so pass around phones and tablets for other designers and the client to weigh in on and approve instead. 

Don’t trust your math, but check type, icon and touch sizes by measuring directly on the phone screen. You can also check for how badly the simplification and lies of the phones and browsers impact you. Classes of display sizes and device pixel ratios mean your design may be 20% smaller or larger on any one device. Make no assumptions about what it will look and act like in the real world. Check yourself.


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=== References ===
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