I strongly recommend using surveys and questionnaires whenever possible.
Asking for feedback from consumers who can critique your provided services, even asking agents in your own real estate office, can prove very valuable to improving the way you do business.
I use the feedback from clients for reviews on my website, in my listing presentation and in my AgentEvaluator® proposals.
It also gives me an idea of what areas I can improve on for future business, as well as track where the leads are coming from.
Of course, I personally call my customers whenever possible. Although email is effective and efficient, I feel a phone call is so much more personal and direct.
In fact, my Broker, RE/MAX Advantage, does a home tour once a week. There are 5 or 6 homes in the same area that we caravan to and critique the home. We fill out a questionnaire to try and give support and suggestions to help get the listing sold. I trust the agents in my office and their feedback and then pass it on to my home sellers.
It has been pretty successful and has helped the sellers realize they need to reduce their price, stage their home, or replace carpet, etc.