One of the easiest ways to keep traffic up at your websites is by adding new content on a regular basis.
Google search results, as well as the search results of Yahoo, Microsoft, and Bing, are all influence by some degree by the freshness, or recentness of the data and information on a website and how recent a webpage was published or substantially edited.
Blogs are one of the easiest types of websites to setup and maintain thanks to publishing platforms like WordPress, and to a lesser extent, Blogger. These platforms take care of much of the day to day work involved in things like webpage design, website linking, and formatting.
They also offer a way to schedule your content to be published at a later date which you define in the interface. This allows you to keep your content fresh without having to actually work on your website every day or even every week.
Instead, write 10 posts all at once and schedule them to be posted over a three or four week time period. Your site will be considered fresh and new the whole time even though it may have been weeks since you actually did anything for the site.
The goal of keeping your content fresh is to move up in SERP, or Search Engine Results Pages. The higher your ranking, the more traffic that will flow to your websites and webpages. More traffic equals more chances to make sales, or more chances to display advertising. Either way, ranking higher almost always means more income.
So, keep it fresh.