This is a classic reference that is worth re-posting. No one seems to know what to do about those pesky open-ended questions you see on a survey. This article offers practical tips on how to handle this type of data.
I summarized this article on my website back in 2005.
O’Cathain, A., Thomas, K.J. “Any other comments?” Open questions on questionnaires – a bane or a bonus to research?. BMC Med Res Methodol 4, 25 (2004). DOI: 10.1186/1471-2288-4-25
You can find an earlier version of this page on my blog.