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Hi Aoife, Vadim posted Google's official response. As a web developer who has worked on many sites over the years I can say it usually takes 1 to 3 weeks for those types of changes to be reflected in the SERP's. What I have found to be true is the more traffic you site has, the more likely Google is to be crawling it. Once crawled however, it still takes time for Google to update the results. Hope this helps, Don

Writing unique and deep content about the subject. For example, If you are targeting the long tail keyword: 'cool buildings found in new york city' and 'the best subway stations in the world.' you should write really good content about the two subjects. Make sure to try to grab multiple long-tail keywords around a certain topic and make sure the content is valuable to your visitors. Not just content created purely for ranking on certain keywords.