Many of the SaaS entrepreneurs I have spoke with have mentioned that contacting prospects via cold emails or calls is very effective for getting brief customer development interviews set up.

When these conversations are positioned as interviews rather than 'research' or a 'survey' people tend to open up more about their biggest business challenges. Creating such a high fidelity connection with customers is difficult to achieve in any other way during the early days of market validation, so pick up that phone and make some calls.

Better yet, get their permission to record the calls, and then post the interview audio and transcript on your customer development blog!

This tactic has worked well for me.