Five tips for better online surveys

1. Every question you ask is expensive. (Expensive in terms of loyalty and goodwill). Don't ask a question unless you truly care about the answer. This means that a vague question with vague answers (extremely satisfied...acceptable...extremely dissatisfied and no scale to compare them to) is a total waste of time. What action will you take based on that? It's smarter to ask, "how much would you say lunch was worth?"
2. Every question you ask changes the way your users think. If you ask, "which did you hate more..." then you've planted a seed.
3. Make it easy for the user to bail. If you have 20 questions (that's a lot!) make it easy to quit after five and have those answers still count. If you waste my time and then don't count my answers, see #2.
4. Make the questions entertaining and not so serious, at least some of them. Boring surveys deserve the boring results they generate.
5. Don't be afraid to shake up the format. Instead of saying, "Here are ten things, rank them all on a scale of one to five..." why not let people compare things? "We had two speakers, Bob and Ray. Who was better?"

Bottom line: before you let the survey guys run a survey of your loyal customer base, make them pay you with resources you can use to reinvigorate those users you just bothered.