Yes, referrals are the best and they have proven to be the most reliable way for me, personally, to get clients. Word of mouth goes a long way. In addition, I’ve had some luck with YourTrainer and have gotten a few long-term clients from it (you can list your profile for free, and pay extra for additional perks/exposure, but I do not do that). I have not been interested in the others you’ve listed, but I do know other trainers who use those resources.
I’ve also found that IDEA has been such a wonderful way to not only get a few long-term clients (I’ve found that most who search using IDEA are potential clients who are serious about using a trainer), but to have an on-line presence and make connections with others in the field and in your area. You never know what kinds of connections you will make and how they could turn into clients. I’ve also had a few companies contact me through IDEA who are looking for trainers. So again, IDEA is a great, reputable resource.
Hope this helps.