Most designers focus on making the UI design more aesthetically appealing; while looks are important what really decides the worth of the UI is its functional design. After all even the most impressive user interfaces can fail if they leave the users puzzled on where to get to what to do with the application.
Derive on the best user interface designs and use simple mockups to create your own UI design over them. Not only does it save time but also results in a perfect combination of form and functionality. Numerous UI mockups are available for download and can be obtained as PSDs to start off with your design right away. Also get other UI elements such as icons, buttons, graphs, sliders and lots more as vectors along with the UI templates and include them in your design as well. Choose from a wide range of interface styles such as Metro, paper style layouts, grid layouts, classic folding interfaces and so on and use these freebies as the base to build up your own UI.