By building the right customer and employee experience strategies and initiatives, I help companies understand their customers behaviours and employees better to make their business more profitable and grow market share. Check out my website (www.michelfalcon.com) to learn more about me and my experience. Also, download my free ebook, "The 28 Traits of Organizations Who Are Customer Experience Titans."
Make it effortless for your customers to do so. Survey them via email and once they have given you a positive review (use NPS to make it simple through radio buttons) push them to a landing page where they can share their message on the discussion forums you wish to profile their review.
I agree with what Dan mentioned. Ask for referrals from existing customers, take speaking engagements to position yourself as an expert and blog. I'm going to try the Google Adwords.
Typically, I ask the client near the end of the relationship once I have produced an ROI. However, if you have a good relationship (client likes you) and have produced small wins, I'm sure the client would refer you prior to completion of the engagement.
Also, plant the seed mid way through the engagement/project to let your client know that you have identified other areas to work together which will increase client retention.
I'll echo what Jason suggested. Focus on your organic growth and customer acquisition. If you're looking for funding, your potential VC's will be looking for customer/community growth and trajectory.
The infrastructure challenge can be solved by purchasing new systems, hiring employees etc. (whatever the challenge is). Not having enough customers or community is a much more challenging and longer process that a VC is less likely to wait around for.
I hope this helps.