Sproull provides some guidelines that might help to increase the response rate of mailed questionnaires:
o include a covering letter that appeals to the respondent's interests, such as ‘as a regular user of the internet, you may be aware….’
o mail a reminder card about ten days after the first mailing; every respondent, except those whose responses have already been received, should receive this
o mail a second questionnaire about a week after the reminder card
o contact non-respondents by phone (or by e-mail)
o enclose a token of identity or an introduction from a person of repute along with the questionnaire
o write clear directions on how to fill in the questionnaire and return it