Hi Ramez,

 I found interesting the attached paper (...and there are a lot of websites providing tips, as you as probably have found).

Hope it helps.

Best,

Ruben.

Hi Ramez,

 I found interesting the attached paper (...and there are a lot of websites providing tips, as you as probably have found).

Hope it helps.

Best,

Ruben.

Rubén, that's a good one!

These references may also help:

1. Edwards, P. J., et al. "Methods to increase response to postal and electronic questionnaires (Review)." Cochrane Database Syst Rev 3 (2009): MR000008.

2. Sheehan, Kim Bartel. "E‐mail survey response rates: A review." Journal of Computer‐Mediated Communication 6.2 (2001): 0-0.

3. Couper, Mick P. "Review: Web surveys: A review of issues and approaches." Public opinion quarterly (2000): 464-494.

Hope they help.

The best source that I know on this issue is Dillman & Smyth, Internet, Phone, Mail, and Mixed-Mode Surveys: The Tailored Design Method.

One way is to offer some reward or incentive for answering, such as offering results of the study, a paper or book that would be of interest to the person answering the study, or a chance to be in a drawing for a prize.