Originally I did spend some time trying to share knowledge about my service. Haven't done so in 3-4 years.
When I did I was doing the usual crappy stuff, sharing on forums, as a signature on posts, comments on reviews of other free survey solutions, and the like. (As I mentioned I'm bad at marketing - so I'm not the best person to answer your question)
If you read the firt part:
http://obsurvey.blogspot.dk/2013/03/how-i-was-forced-to-crea...
You'll see that the growth is mostly word of mouth.
