The kind of content you create depends on your audience's needs at different stages in the buyer's journey. You should start by creating buyer personas (use these free templates, or try makemypersona.com) to identify what your audience's goals and challenges are in relation to your business. On a basic level, your online content should aim to help them meet these goals, and overcome their challenges.
All sites have a home or "root" page, which is usually the most frequented page on the site and the starting place of navigation for many visitors. Unless your site has only a handful of pages, you should think about how visitors will go from a general page (your root page) to a page containing more specific content. Do you have enough pages around a specific topic area that it would make sense to create a page describing these related pages (for example, root page -> related topic listing -> specific topic)? Do you have hundreds of different products that need to be classified under multiple category and subcategory pages?
Social media marketing involves the use of social networks, consumer's online brand-related activities (COBRA) and electronic word of mouth (eWOM) to successfully advertise online. Social networks such as Facebook and Twitter provide advertisers with information about the likes and dislikes of their consumers. This technique is crucial, as it provides the businesses with a "target audience". With social networks, information relevant to the user's likes is available to businesses; who then advertise accordingly. Activities such as uploading a picture of your "new Converse sneakers to Facebook" is an example of a COBRA. Electronic recommendations and appraisals are a convenient manner to have a product promoted via "consumer-to-consumer interactions. An example of eWOM would be an online hotel review; the hotel company can have two possible outcomes based on their service. A good service would result in a positive review which gets the hotel free advertising via social media. However, a poor service will result in a negative consumer review which can potentially harm the company's reputation.
SEO today is in many ways still a focused and specific discipline requiring experience and expertise. However, it has become much more dependent on, and integrated with, other digital marketing channels which is a good thing allowing for the scaling of content and resources. As most marketing is now digital, SEO has a proper seat at the table and place as a lead organic traffic driver contributing to end business goals.
Digital marketing is defined by the use of numerous digital tactics and channels to connect with customers where they spend much of their time: online. From the website itself to a business's online branding assets -- digital advertising, email marketing, online brochures, and beyond -- there's a spectrum of tactics that fall under the umbrella of "digital marketing."