The cornerstone of SEO is having great quality content matching what your potential customers are searching for. I can’t emphasise that enough, neither can Google, Bing and the other search engines. If you can’t find the time to research and add new content, then you are missing a huge opportunity and crippling your online business potential.
Find what people are searching for by using Google’s keyword research tool: https://adwords.google.com/o/KeywordTool
Or Bing’s keyword research tool: http://www.bing.com/toolbox/keywords
Even if you’ve done research previously, take some time out to hunt for new ideas.
TIP 1: In Google’s tool ensure you have phrase not broad match selected.
TIP 2: Don’t bother with the Bing tool, it is totally useless!