1) ‘Speak’ the search engines language: It makes more sense to start with on-page SEO and get it right rather than trying to convince search engines to give you better ranking with off page SEO. Search engines are computer programs (software) and they understand a particular language. With SEO and especially on page SEO you ‘speak’ their language and your goal is to help them understand what you website is about. In other words the more signals you can give them, the more are your chances of achieving better rankings.
2) On Page SEO is about the user as well: Never forget that your primary target is to keep your users happy. Off Page SEO may bring traffic to the website but if it is not setup correctly, if it is not user friendly the results will be disappointing.
3) Many websites get it wrong: It’s amazing but it is true that the majority of websites today are not optimized for search engines. Despite the plethora of information about SEO many website owners believe that it does not worth to even do SEO and they quit before starting. For those cases on-page SEO has a lot to offer both in terms of usability but in terms of traffic as well.
4) On Page SEO is sometimes all you need: If you are running a website for a small business and you need to get local customers searching for various terms on Google then on page SEO is all you need to do.
5) Off page SEO comes after on page SEO: In order to start thinking on how you can promote your website you need to be sure that the website is optimized and in good condition. So the first step is to work with on-site SEO first and then go off-site.