Ask HN: Advice with running market research surveys?

What's your best advice or experience as far as running market research surveys?

- What are survey design tactics for enticing the most people to respond honestly to my survey?

- Do you typically run more surveys often, or fewer longer surveys? What works best?

- How well do giveaways work to incentivize responses? iPads are the token giveaway - does one big prize tend to work better than several smaller giveaways?

- Is it a good idea to gently remind people to respond to a survey, or is that just annoying?

- What creative ideas have you tried to get more responses, and what were the results?

Thanks for any pointers here. (: