Most of my SEO clients already have an existing site. It is my job to take what I am given and do my very best to ensure that it starts ranking well for the chosen keywords. Normally this would entail at the very least, changing Metas, adding some relevant content and keyword placement. The problem is, by adding content and making small changes it is very easy to make an existing site look a little spammy especially if the site was never designed to have content on the home page.
I believe that the following 3 broad points should be taken into consideration when designing and implementing a new website to ensure that it is given a good SEO foothold:-