SEO can be broken down into offsite and onsite. Offsite is simply not on your website and onsite is, yeah, you guessed it, on your site. You can hire a SEO company or person to do offsite SEO for you and they never need access to your site. Offsite breaks down into these important things.
Blogging (Fresh Content) – Blogging for SEO purposes can be done onsite or on another blogging platform like Blogger or WordPress. A blog post is an article written about your website/business. Having the blog post to different pages of your site using different highlighted text sections of the article (Anchored text links) can be very effective.
Backlinks – Your website gains Google search engine position or rank with the quality and quantity of the links you have pointing to your site from other sites. Sites based on similar areas/topics can really help one another by linking to each other.
Business Directories – Sites like YellowPages.com, YP.com, Yelp.com, and AngiesList.com are a great place to have your business listed.
Social Media – Every social site is being tracked very thoroughly by Google amongst other entities. Every time some shares, hashtags, likes, follows or even mentions your site, Google knows. Having people engaged and sharing content via Facebook.com, Twitter.com and Instagram.com is a very good thing.