How would you promote a new startup?

You didn't mention anything about Youtube or Google +

You can try and utilize those two also especially for SEO

 

Submit to startups site. Try eStartups.org, that's my site

 

Create accounts in social networks, register on forums, submit a press release to PR websites, post on review websites, write articles for blog and promote them, send newsletters, add video to Youtube. All those points can be done on your own without huge investments. If and when you get more profit, you can develop a mobile version of the website or a native mobile application. That will help reaching clients who prefer mobile and tablet browsing.

 

[FONT=Liberation Serif, Times New Roman, serif]Social network presence is important. Create Facebook and Twitter pages, submit a press release to PR website, publish a review on review website, make announcements on forums and blogs. After your startup becomes popular, create a mobile website or a mobile app to access customers on the go.[/FONT]

 

Yes, social media is the one of many ways. But, ensure that you find people/community who interest with your product.