I would say find your target market on twitter and start following people. Hpefully they will follow you back. Then just make sure to send out informative tweets to them. Also to find clients, search keywords like "virtual assistant" or whatever specific service you provide. You will often find someone looking for services that way. I tried that a few weeks ago and it worked. There were a few people looking for General VA's but I wasn't interested in those positions, ie outbound calls, etc.