SEO is a very democratic word in now days. Google hates seo because it manipulates its results. But it became need. Many companies are providing seo services. They use different –different techniques to improve the rank of website. Every website wants to payoff these services to come on the top position.
You have to do your best and sensible efforts to come on the top because your competitor is also taking payoff of these services. Question is originating that which thing will create difference between you and your competitor. That’s your efforts which arises your position compare than your competitor. Many company use ethical techniques and many uses unethical. If you want to see your website in beneficial position then you have to use ethical techniques. A new website can get popularity by the help of seo services. So these techniques are facilitating for new comer in the web. 
Google says that it will block all seo activities in future. But no one know that what happen in future?
In seo you have to prove each and every method by practical because there is ambiguity in methods.
Now we take look of these factors that affect the rank of website on the SERP. Basically there are two factors first one is on-page factor and another one is off-page factor.
In on-page factor we can include H tags, Meta tags, web page content and threw these factors we can improve in the rank of website.
Link building, Article submission, blogs, forums all of these are in off-page factor.But spite of that there are few more factors which also effect the rank of website like user behavior, relevancy (Geo-graphically) etc.
But finally seo is a wide field and you have to update yourself about this.
