An example of SEO for Middleman sites. Add data (like titles, meta descriptions, etc.) using YAML files and frontmatter, and use custom helpers to process the data and display them properly within your ERB layouts and partials.

_head.erb

<title><%= title_helper %></title>

<meta charset="utf-8">
<meta content="IE=edge,chrome=1" http-equiv="X-UA-Compatible">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="description" content="<%= description_helper %>">

<link rel="canonical" href="<%= permalink_helper %>">
<link rel="author" href="<%= data.site.gplus %>">
<link rel="alternate" type="application/rss+xml" title="http://feeds.feedburner.com/derekconjar">

<meta property="og:locale" content="en_US">
<meta property="og:title" content="<%= title_helper %>">
<meta property="og:description" content="<%= description_helper %>">
<meta property="og:url" content="<%= permalink_helper %>">
<meta property="og:site_name" content="<%= site_name_helper %>">
<meta property="og:image" content="<%= image_helper %>">
<meta property="og:type" content="article">

<meta name="twitter:card" content="summary">
<meta name="twitter:site" content="<%= data.site.twitter_handle %>">
<meta name="twitter:creator" content="<%= data.site.twitter_handle %>">
<meta name="twitter:title" content="<%= title_helper %>">
<meta name="twitter:description" content="<%= description_helper %>">
<meta name="twitter:image" content="<%= image_helper %>">

<meta name="google-site-verification" content="nnaAbi0PPS-NaF_f_sIM83C12Zh_JV3GNqzR52gtdao">

<link rel="shortcut icon" href="/images/favicons/favicon.ico" type="image/x-icon">
<link rel="apple-touch-icon" href="/images/favicons/apple-touch-icon.png">
<link rel="apple-touch-icon" sizes="57x57" href="/images/favicons/apple-touch-icon-57x57.png">
<link rel="apple-touch-icon" sizes="60x60" href="/images/favicons/apple-touch-icon-60x60.png">
<link rel="apple-touch-icon" sizes="72x72" href="/images/favicons/apple-touch-icon-72x72.png">
<link rel="apple-touch-icon" sizes="76x76" href="/images/favicons/apple-touch-icon-76x76.png">
<link rel="apple-touch-icon" sizes="114x114" href="/images/favicons/apple-touch-icon-114x114.png">
<link rel="apple-touch-icon" sizes="120x120" href="/images/favicons/apple-touch-icon-120x120.png">
<link rel="apple-touch-icon" sizes="144x144" href="/images/favicons/apple-touch-icon-144x144.png">
<link rel="apple-touch-icon" sizes="152x152" href="/images/favicons/apple-touch-icon-152x152.png">

<%= stylesheet_link_tag "all" %>

<!--[if lt IE 9]>
  <script src="https://oss.maxcdn.com/libs/html5shiv/3.7.0/html5shiv.js"></script>
  <script src="https://oss.maxcdn.com/libs/respond.js/1.3.0/respond.min.js"></script>
<![endif]-->

search_engine_helpers.rb

module SearchEngineHelpers

  def title_helper(article = nil)
    if article.nil?
      if current_page.data.title.nil?
        "#{data.site.name} - #{data.site.tagline}"
      else
        escape_html(current_page.data.title)
      end
    else
      escape_html(article.title)
    end
  end

  def description_helper
    if current_page.data.description.nil?
      escape_html(data.site.description)
    else
      escape_html(current_page.data.description)
    end
  end

  def permalink_helper(article = nil)
    if article.nil?
      data.site.url + current_page.url.gsub("index.html", "")
    else
      "#{data.site.url}#{article.url}"
    end
  end

  def image_helper
    data.site.url + '/images/' + current_page.data.image.to_s || nil
  end

  def rss_link_helper
    data.site.url + '/feed.xml'
  end

  def site_name_helper
    data.site.name
  end

  def sitemap_entry_helper(page)
    data.site.url + '/' + page.destination_path.gsub('index.html', '')
  end
  
end

site.yml

url: "http://www.example.com"
name: "ACME Widgets"
tagline: "Best Widgets in the Universe"
description: "Default meta description"
gplus: "https://plus.google.com/XXXXXXXXXXXXXXX"
twitter_handle: "@acmewidgets"

sitemap.xml.erb

<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
<% pages = sitemap.resources.find_all{ |p| p.source_file.match(/\.html/) } %>
<% pages.each do |page| %>
  <% if page.url.include? "/thanks" or page.url.include? "/404" %>
  <% next %>
  <% end %>
  <url>
  <loc><%= sitemap_entry_helper(page) %></loc>
  <priority>0.8</priority>
  </url>
<% end %>
</urlset>

what does your config.rb file look like for this project? Middleman isn't picking up the site.yml and search_engine_helpers.rb files for me. I'm assuming I need to add something to my config file but I'm not sure what