Auto-suggest
Everytime it is possible, the form provides a field list instead of a string field. Everytime a post code is needed,for instance, the user will find a field "list". Typing the first letter or number in the field only, the corresponding results in the list will appear, leading the user to the right selection. In this way, you both reduce the time needed to fill in a form and reduce the chances of submitting forms that contain unintentional mistakes