How to get valuable feedback from your users?

Hello Hackers!

Jose from WebDab Here. Six months ago, I started working on this site: webdab.com. I needed something similar for one of my projects, but I found the options out there were waaay too expensive; I couldn't afford any.

So, I started building my own thing. Initially, it was only the backend, then I created the front end and set it up as SAAS. My solution It's an easy in-depth social analytics service.

At the moment, I have my service live and running with a decent amount of free users. And recently, I've been running into the "talk to users -> get PMF Loop". However, getting feedback from users has become quite a challenge, and I'm thinking about sending an online survey to understand my customers' needs.

I was wondering if it's a good idea to use an online survey to get feedback? Anyone here at IH has any experience with this? If you don't think it is a good idea, can you please suggest other methods to get feedback from your users?

Also, I'm planning on offering a small incentive, i.e., a $10 - 20 amazon voucher. Not sure if this is also a good idea. Do you offer any incentives to your users when asking for feedback?

If you use a survey, what sort of questions do you ask?

Will one single question work, i.e., would you recommend us to a friend?
Or is it a good idea to ask more questions?

As you can see, I have many doubts on this matter, but I think this is the right place to ask these type of questions. Please let me know if you had any experience getting feedback from your users.

Thanks in advance; Your comments, observations, or suggestions are highly appreciated.