There are many factors that need to be considered whenever evaluating an SEO Company for your website. Everything from what and how they perform their work to cost and long-term results will play an important role in the long term success.

Here are some important questions and thoughts to consider:

Choose a Local SEO Company

By choosing a local web marketing company you can visit their offices and meet their people easily. It is also easy for them to visit your business and get to know you. Trust and a good relationship is a very important aspect in choosing an seo vendor. A company in another state or country is often harder to reach and they are often not likely to have your best interests in mind.

Specialist in PPC and Organic Optimization

Is this company familiar with the different Pay-per-Click programs (Adwords, MSN AdCenter, Yahoo Search Marketing, etc.) and Organic Optimization? Depending on your budget, objectives and time frame, both type of programs may be necessary to achieve your goals. It is not uncommon for large websites, targeting 1000s of keywords, to use adwords (or similiar) and to aggressively target organic optimization.

Define Your Key Performance Indicators / Objectives

Sit down with your potential web marketing vendor and talk about all of the different performance goals that you want to consider and improve upon. Can they track your Bounce Rate (website and each web page), New Visitors, Top Phrases driving your website traffic? The Key Performance Indicators (KPIs) that are important to you are often different than your SEO Company. Talk to them about the things that are important to you and make sure you understand how those goals are going to be achieved.

Long Term Approach

Are they simply charging a low fee (ie. $29.95) a month for "submitting" your website to search engines? Or are they actively providing you with recommendations for your website and increasing your keyword rankings over time?  Submission programs do NOT work. All of the major search engines constantly revisit websites, including your own. It is a waste of your marketing budget to simply pay for something that is done automatically.
It is important to look for a company that will make site recommendations, perform keyword research and analysis, provide keyword ranking reports, competitor analysis and monitoring, visibility improvement and other optimization techniques.
Although keyword ranking reports are important, they should not be the only measurement of success.  It is very common for keyword rankings (or SERPs) to move up and down every day, so monthly keyword comparisons often doesn't give you all of the full picture. You need to look at the success of your overall campaign and all of the Key Performing Indicators that you defined at the beginning of your campaign.

SEO As A Part of Your Marketing

Can the SEO Company work with your Marketing Department to plan and develop coordinated programs? Website Optimization and Marketing is really a part of your company's complete marketing program.  Your SEO company should be communicating with your Marketing Director to learn how his initiatives complement their tactics.

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Choosing an SEO Vendor is not an easy task. Trust and responsibility are a requirement as it is your website and company that visitors see.  You need to screen them carefully, make sure that their qualifications and skills match with the goals of your organization.  Look for a long-term approach that concentrates on other factors besides simply ranking for keyword terms.