Write articles rich in content. Quality articles will get ranked better in search results. Make sure that your articles address the needs of your readers, and that they can find all of the information they need in one spot. This is the most effective means for increasing traffic to a website; offering people something that they cannot obtain elsewhere, or at least, not to the level of quality that you are offering it.
Do not be fooled by those traffic sellers promising thousands of hits an hour. What they really do is load up your URL in a program, along with a list of proxies. Then they run the program for a few hours. It looks like someone is on your site because your logs show visitors from thousands of different IPs. What happens in reality is your website is just pinged by the proxy, no one really sees your site. It is a waste of money.