Welcome to the Q&A Forum

I would disagree to an extent. Whist it may be a factor if you go buy an old domain and build new content on it Google pretty much treats it as a new domain and along with that if all the links going to that domain are for example about cats and your domain is about dogs you're making your life harder. Matt Cutts mentioned here that its not something you should worry about, now while he neither confirms it, nor denies it what it does indicate are there are other areas to focus on. So in short if the domain is the same niche and the links already built are a benefit the the user (who may get to your site from those links) then it should be fine but at the same time is it worth the risk of moving a whole site? There are many good ways of indexing a site which is a lot easier than a redirect. Work on the content of your site, get it shared (even socially) and you will find it ranks quicker (also try 'Fetch as Google') than just redirecting a domain to it (or visa versa) Hope that helps.

Here are a couple of posts about performing an audit on your site to help diagnose problems, and they may help get you started: http://moz.com/blog/how-to-perform-the-worlds-greatest-seo-audit http://moz.com/blog/how-to-do-a-site-audit