You cannot set up a successful internet business without a good mailing list, but the problem that many start ups face is that they need to generate money fast and list building takes a long time. This is a reason why so many people fall into the trap of buying lists - not only are the validity of the email address doubtful, the huge list will include only a few people who are really interested in what you have to offer. There are some list building techniques you can use to speed up the process and the first of them is Search engine Optimization or SEO.
SEO is nothing more than making your site as relevant as possible to search engines so that you appear high up on the search results which means that the number of visitors you have will be large. But getting visitors is not getting business - that will come later after you start sending them sales emails based on the email addresses they leave with you in return for a free download that they will get in return for their addresses. What you offer is very important and the most common of these freebies is an ebook that will be of interest to your target market - those who leave their email addresses are those who are interested in what you are selling.
You could also use a splash page to get addresses - many people think that these are annoyances but remember that Barak Obama used had one on his website during his presidential campaign and look at where he is now. A splash page is like a forward to your website with a catchy headline and an offer of sending people interesting information in return for their email addresses - information in terms of a news letter that only indirectly talks about your business (you can't be direct because you offered them information, not a sales spiel). Once you have these addresses you can use them for sending out newsletters and articles that will indirectly sell your products as well as for direct selling mails.
Do not overlook the potential of offline list building techniques. Ask your friends and relatives for the email addresses of their friends and business contacts -and when you email these people tell them how you got their addresses. Seeing the name of someone they know will cause people to pay more attention to your email and that is the key to attracting their interest.
Spend time learning other list building techniques but using these can provide you with a good start - but do not expect overnight results: there are no list building techniques that can offer that.