As with most consulting services, it is hard to provide a “standard” service that will fit all businesses. When it comes to SEO, one size definitely does not fit all.
Each website is different. There are no identical websites anywhere on the Internet. Because each site is different, and the goals that each website owner wants to achieve are different, then the tactics or practices that a SEO service firm must take in order to gain the most visibility are necessarily different.
The types of services that you might see promoted are on-page optimization, off-page optimization, link building, social promotion, penalty recovery services, image optimization and countless others. Each of these services has its own particular set of skills that must be mastered in order to achieve the optimal result for a client. Some people are good at link building, others are better at content optimization. Still others are good at website structure which contributes to user experience which is also a ranking factor.
When you are looking for a SEO firm to improve your web traffic and rankings, make sure you understand what you are paying for, i.e. what services are you getting? If you are only interested in the result, then you are leaving it to the SEO firm to choose which tools in their tool belt they will employ to achieve your desired ranking. If you are paying for one service, then understand that that particular service may improve your rankings, but may not get you to the top of rankings because there are other things that are going on with your site that may prevent an optimal outcome.
We always advise our potential clients to have a site audit performed before they, or their chosen SEO consultant, do anything. A site audit will indicate where there is room for improvement and where there are problems. This will inform which services are needed to get the desired result. Just buying “SEO consulting services” without a plan for success will surely result in disappointment on both sides of the transaction.