Consider how well you know your industry. If you have been in business for a while and already know what your customers want and how to best reach them, you may want to start to build a long-term SEO strategy that will provide value over time. If you aren’t sure how customers and competitors will respond to your offerings or content, you may want to consider an SEM campaign that allows you to test your ideas, products, and services. Use these sites for market research to better understand your target audience and your position in the industry.
The SEO starter guide describes much of what your SEO will do for you. Although you don't need to know this guide well yourself if you're hiring a professional to do the work for you, it is useful to be familiar with these techniques, so that you can be aware if an SEO wants to use a technique that is not recommended or, worse, strongly discouraged.