Referrals are excellent. your website is another excellent way. Of course, just any plain website without proper SEO is not going to do even the most remarkable service/product any good. There are many good ways online and you should have Page 1 ranking on Google to get maximum exposure. Many companies will tell you alot as I've learned but not deliver much. More info about your product or service would help.My company has many top 1 ranking on Google for many of the keywords.
Ken