Provide keyboard accelerator shortcuts for expert users. Though mainframe and terminal based applications may be harder to learn, over time, the speed of keyboard navigation can be impressive. Web based applications need not lose this possibility of efficiency - leverage keyboard shortcuts to give power users lightning fast efficiency.
Consider Twitter's set of keyboard shortcuts below.
Consider Expedia's flexible search options below. Common destinations are shown as radio buttons, but a free-form option is also available.
Consider Google Calendar's weather information below. It does not complicate the interface, but puts highly desirable information at a user's fingertips.
Anticipating a user's possible needs and provide easy actions. In Gmail, if you label a piece of mail as spam that it knows how to unsubscribe you from, it will give you the opportunity to authorize it to directly. A warning: if you attempt to implement proactivity, you must do it well. People generally do not like proactive interfaces that distract, interrupt or break flow or provide irrelevant information.
Don't "gold plate" an application with options that will never be used. User research and usability testing can help validate actual vs assumed needs. Consider the below picture of a user hacked remote control that only exposes the buttons that they needed.
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