Thats marketing... and there are a lot of ways to skin that cat.
Cold Calling is virtually dead in the traditional sense (for Small-Medium business). Cold Emailing can work, but there's a lot of noise with all the SEO scams that business owners get.
For Marketing, I generally recommend doing something that you are good at that other developer's don't do. Stuff like networking events, public speaking, Business Clubs(Vistage, etc), etc. Indirect approaches work really well too- Partner with a bar for a "business happy hour" and buy everyone's first drink, then literally go business to business (of businesses that have websites you would like to redo) and invite them. A similar sort of a thing, with less personal interaction is to build a website that would directly benefit local businesses and give it to them for free. Targeting is important.
These sorts of things are really only for when you are starting out though (1 year tops). After a year of these sort of gimmicky things you should have built a solid portfolio and should focus your energy on growing your business via your existing clients. They should be ecstatic to give you more business because you took care of them so well.
