Most Web sites have some kind of form for visitors to fill out -- registration forms, contact forms, feedback forms, order forms and more. But forms are time consuming and often perceived as an interruption or annoyance by the user. That’s why your forms need to be as easy to use as possible; otherwise they can spoil the user experience and affect your bottom line.

To create a user-friendly experience, make sure you choose the most appropriate of the five HTML form elements available:

1. Drop-down box. Drop downs not only make a form look shorter but they are the best choice when users need to choose from a long list. Use them especially when the answer to your question is unfamiliar and/or easily mistyped. Keep options short, concise and easily readable so user can quickly scan the list.
2. Radio buttons. Many users don’t know this, but when using radio buttons, only one choice is possible. Pre-populate the most likely choice as a default, then make it clear another choice can be selected instead.
3. Check boxes. As with paper forms, check boxes allow a user to click all or no acceptable choices. Use checkboxes (or radio buttons) when the number of possible selections is 4 or less.
4. Type-in box. Use when typing the selection is more natural to the user than selecting it from a list. Perfect for a user’s personal details and for situations when the options look similar, such as numbers 1-10.
5. Hyperlinks. Used less frequently but it’s relatively clear that the choice is to click one of the optional links.

For more info: see Carolyn Jarrett’s Forms that Work

http://www.formsthatwork.com/papers.html