How does practical marketing work, then.
The non-answer: it depends.
In the early stages, few startups would hire a dedicated marketing person because the founders or entire teams does marketing depending on your marketing philosophy. For web startups, working your network in extending outward circles - tech friends, industry colleagues, specialized media - has been the established method to from stealth to viral. Working blogs, forums and other hangout in your industry is another approach by which you can build a good reputation and find potential customers. But dedicated, high quality community outreach is resource extensive and difficult to pull of if your industry is big.
If you are a very tech oriented guy, you might want to partner up with a passionate business person to get some needed perspective. This way you will have a co-founder and a more marketing oriented person in your startup.
Twitter exists. Use it. Write meaningful content about your startup, products, office, thoughts on your industry, etc. Befriend and interact with people in your business. Reply to their tweets, ask questions.
Facebook exists. Use it. Just remember that dedicated community outreach is resource expensive. Plan for it.
Never underestimate the Silicon Valley effect. Working=living in the area and hanging out with the right people can be a tremendous marketing advantage. If I lived in the USA and was about to launch a serious startup, I would definitely consider moving to The Valley.
