Full-time researcher here, with some further advice:

1. If there is any way to get a properly qualified researcher, there is absolutely no substitute for doing so. Research is a specialist skill, so attempting to do your own research without the requisite background is like doing your own plumbing - you can do a few simple things on your own, sure, but you will need to bring in the professionals for the trickier jobs. Discovery research - finding out what your users' needs and problems are - is one such very tricky area.

2. Don't just believe them. They are trying to please you, and will say absolutely anything they think you want to hear! I actually overheard this conversation once:

"Can you think of a situation where you'd use this app?"

"I ... uh ... I mean ... I might use it if I couldn't [use normal method] and had a particularly tricky use case, maybe."

He wrote down "would use it if ..."

(WTF?!!!)

I wrote down "this customer absolutely would NOT use this product."

3. Read The Mom Test (Rob Fitzpatrick) for a more detailed breakdown of exactly why your customers are lying to you, and what to ask instead.

4. Use a funnel structure - start with broad tell-me-about-your-day questions and then move in to more and more specific questions, grounded in concrete examples of when they last did something, not what they hypothetically might do.

Happy researching!