Here are a few tasks and areas that you should consider each month, to ensure that you keep on top of your optimisation. Turn them into an action plan, and review them regularly.
Keywords – target mid-range keywords that have less competition yet are still relevant to your site. Also check out both mass-market and niche competitors, to see which keywords to use and which to avoid (niche keywords might produce little opportunity for your site).
Competitor Analysis – tools like trends.google.com and www.compete.com can help you to identify key operators in your market. Analyse the homepages of their sites to see whether you can utilise anything to improve your own ranking.
Products and Services – you should regularly review your portfolio to see if you are missing any opportunities to add something that might bring in new business – not just more of the same offers you already have!
Twitter – if you're not there, then think about getting a presence. Use tracking links in your tweets to monitor the clicks you're getting, and make sure you post some tweets that are not pure marketing. It does no harm to show a human side once in a while!
Multimedia – turn some of your articles or blog posts into video, and post them on your site and also on YouTube.
Site Content – you should be adding keyword posts every day. Make sure you have balanced content in terms of text and links, and design pages with the most important information at the top.