Trying to improve search engine rankings is just like a rubics cube. A puzzle that can keep you occupied for hours. How many times have you heard "They keep changing rules?,” and frustrating part is...they don't even tell you what rules are in first place!
It's a proven fact, in trying to improve search engine rankings, that growing your site thru link popularity, by slowly acquiring incoming quality links, adding small amounts of fresh relevant content on a regular basis, using proper keyword density and placement, along with making your site "sticky" so your visitor's stay longer.
But now, there's something else that you have to know about! (and this is a big but!)
Google is starting to weigh in heavy on domain names. Not what your domain is, or how long you've had it. Google wants to know how long you plan on keeping it, as in, how long is it registered for!
They've begun NOT giving as much consideration to domains registered for just a year, thinking they might be spammers, making a quick hit and then they're out of here. If they see you're registered for 5 years, then you must be a serious business that has planned on being around for quite a long time.