Sure, ad extensions can produce additional leads and the display network provides value to the top-funnel searches, but if you get the three core assets right and have an experienced team that knows how to manage your bids and budget, you will continue to win, no matter what SERP layout changes Google throws at you, such as the elimination of the right rail.
Description meta tags are important because Google might use them as snippets for your pages. Note that we say "might" because Google may choose to use a relevant section of your page's visible text if it does a good job of matching up with a user's query. Adding description meta tags to each of your pages is always a good practice in case Google cannot find a good selection of text to use in the snippet. The Webmaster Central Blog has informative posts on improving snippets with better description meta tags18 and better snippets for your users19. We also have a handy Help Center article on how to create good titles and snippets20.
Digital marketers monitor things like what is being viewed, how often and for how long, sales conversions, what content works and doesn’t work, etc. While the Internet is, perhaps, the channel most closely associated with digital marketing, others include wireless text messaging, mobile instant messaging, mobile apps, podcasts, electronic billboards, digital television and radio channels, etc.
Another excellent guide is Google’s “Search Engine Optimization Starter Guide.” This is a free PDF download that covers basic tips that Google provides to its own employees on how to get listed. You’ll find it here. Also well worth checking out is Moz’s “Beginner’s Guide To SEO,” which you’ll find here, and the SEO Success Pyramid from Small Business Search Marketing.