Limit the number of fields 
Long forms with lots of fields to fill out tend to scare users away because they think filling out the form will take too much time. The best way to encourage users to fill out a form is by keeping the form as short as possible and by only asking for information that is strictly necessary. For private persons this information consists of a name, address and e-mail address. For companies placing online orders, you should also ask a VAT number and company name. Don't ask for things like a term of address, like a lot of Belgian sites do. INNO for example offers users a list of no less than 24 possibilities, including 'Professor' and 'Count and Countess', which is of course completely unnecessary.

Put related information together 
Instead of asking for the information in a large number of different fields that are placed underneath one another, it is best to only use one field for things that belong together anyway. For example, instead of using two fields for first name and last name, you're better off providing one field for 'name'. The same goes for street and number, which you can ask for in one field as well. If you prefer - for database purposes - to receive all the information in separate fields, then don't put them underneath one another but put the fields that belong together on the same line. That makes the form look shorter and gives users the impression they have to fill out fewer fields.

Indicate which fields are required 
A lot of users are very reluctant to leave personal information on a web site and they often try getting away with filling out the fewest number of fields possible. Provide users with instructions at the top of the form by saying something like: "Fields marked with an * are required." and put an * before the required fields. Make sure users can see at a glance which fields are required and which aren't so they get a good idea of how long it will approximately take them to fill out the form. That way, you minimise the risk of mistakes and increase the user's chance of correctly sending the form at his first attempt.

Don't make too many fields required
Be careful not to indicate too many fields as required fields. Try to keep the required fields limited to the user's name, address and e-mail address. Indicating too many fields as required doesn't mean you get more information, but that you're more likely to get false information. Another thing to be aware of when indicating required fields is that you should make sure you don't exclude potential customers by making certain fields required. For example, if you ask for a phone number, make sure the user can choose which phone number he provides (home, work, cell phone, …). A lot of people only have a cell phone.

Els Aerts & Karl Gilis