Before you can decide to use the contingent valuation methods, it is worth clarifying your objectives and mostly the context (including the nature of the goods being analyzed) which you intend to apply the WTP methods. There exist several methods, including contingent valuation that you need to review and make your choice accordingly. I have come across an interesting review of WTP methods and you can check at: http://michael.hahsler.net/research/wtp_innovative_marketing2006/wtp_breidert_hahsler_reutterer_preprint.pdf
As you know, economic agent can be preference can be revealed or stated, depending on the nature (public, quasi-public, private) of the good be analyzed.
The model you use can be decided based on the assumptions and data availability. usually we get qualitative data in such research issues (WTP). we may use logit model.