Exactly the same way it's tough to buy an automobile if you know nothing about what it should seem like underneath the hood, it is a bit intimidating to pay for a SEO company if you're not exactly sure what distinguishes the good in the bad. Since search engine algorithms are extremely temperamental, you need to ensure you are getting a company that is experienced and up-to-date; otherwise, all the services you taken care of could go out the window as quickly as the next Google update is rolled out. Here are some tell-tale signs to watch out for - if your company does these, you might want to forgo hiring them.
In case your company promises you an unreasonably large number of articles, blogs, links, social bookmarks, etc per month, you must back away. Google wants genuine, organic content - not something which has been spewed out with a program in broken English and questionable grammar. These 500 articles and 1,800 social shares might look appealing, but if they're not written by a human, they can do more damage than good.
No references or examples:
Prior to hiring a business, ask to see what they were able to do for other clients. They should have some kind of track record, some way of demonstrating their work continues to be successful in the past. Any good Search engine optimization company keeps visual records and statistics of progress with time to show to their clients. If they don't leave a paper trail of any sort, try to escape!
They are not well-rounded:
The organization should push not only higher rankings; they should be also promising more sales, more site visits, more Twitter followers, et cetera. Sure, getting your page show up on the leading page of Google's results is awesome, but if no one is clicking on the link simply because they will easily notice it isn't useful or relevant, it doesn't really help you any. The best goal is to produce a better representation of the logo and to create a good reputation with visitors to the website.