Ask HN: What's the best way to crowd source data?

I'm starting work on a side project but in order to get it off the ground I need to gather quite a bit of data. I'm going to crowd source it and was wondering if anyone has any advice on the best way to go about it? Also I don't know how willing people will be to help, do you normally have to give some kind of incentive?

I'm not after that much data from each person just 8 to 10 quick questions however what I'm asking for is quite personal e.g (job description, age, salary etc) so I guess I need to make sure people can submit data 100% anonymously.

Any help would be appreciated.