Use colour strategically. Colour in forms should be used with care - but used well it can really aid form completion and navigation. In general, yellow, for example, is a colour to avoid as much as possible - text set in yellow on a typical light background can be very hard to read - and people can find yellow aggressive.
How does a sinkhole form
Provide examples of the sorts of answers you are looking for, and where appropriate, provide guidance notes as near as possible to the question they relate to (i.e. in the actual form).
Also make sure that you make good use of features like running headers and footers on every page to remind people what the form is, where they are, and what page number they are on.
Use appropriate response mechanisms. Paper forms have the disadvantage that users can miss, or simply disregard, an instruction. For example, only tick/check one box from a list of 15 or 20 options.
When designing forms make sure the response mechanism is appropriate to each question. Having gone to all the trouble of filling in your form, the least you can do is provide users with information about what happens next. Customer communication is key, and since you have made the form so easy to fill in and return, processing it could also be a breeze!
More System Windows Forms Best Samples
Text alignment in labels on a windows form how do i make system forms webbrowser alternative 1