What measures should sociologists take in order to ensure a high response rate in mailed/postal questionnaires?

Sociologists should make the mailings attractive, easy to read, as well as easy answer and send in. Including postage, or using e-mail, may increase response rates. The sociologists should also make the questionnaires on topics of interest to people, not too long, while explaining the study well, even offering to send later information when the study is complete if feasible.