UI Basics - Few gudelines

“A good designer knows the user and designs for the user”

The user interface is the aggregate of means by which people (the users) interact with a particular machine, device, computer program or other complex tool (the system). The user interface provides means of:
• Input, allowing the users to manipulate the system
• Output, allowing the system to produce the effects of the users' manipulation.

- Wikipedia encyclopedia

The following list is a compilation of some basic guidelines every designer will follow and some of my personal experiences.

Even before that, there is one point which I would emphasize -
It is not enough if a design is aesthetically pleasing it should also be technically flawless.

1. Know your user and understand their profile (requirement gathering, persona creation and other usability tools)
2. The client is not always the end user. If you feel a certain element is essential in terms of the user, let the client know about it.
3. Follow consistency in terms of placement, color, functionality etc.
4. Make visual cues clear.
E.g. if link text are underlined, do not underline submenus or titles. This will confuse the user.
5. Know how to attract attention. Animated gif or a promotional tool should be attractive at the same time be in sync with rest of the page.
6. Use css and html to give optimum results. Understanding of SEO basics and css2 go a long way in making a good website.
7. Provide Help to the user.
About boxes, help documents, tool tips, visual cues etc (feed back to say action is complete).
8. Visually define the context. Cancel and refresh buttons placed together in a form generally created confusion.
9. Give importance to typography. Defining correct font size for headers, sub-headers and other text help the user to a great extent.
10. Use proper metaphors when you design icons.
11. Use controls effectively. (Radio button, check box etc.)
12. User testing is an absolute essential.

This is not an exhaustive list. Comments and suggestions are welcome.