Just Google/Yahoo the words, "SEO companies in 'your city,'" or some type of keywords similar to those.

You will get freelancing or SEO company' s websites for SEO, just decide your budget and action plan and post on these freelancing sites.

-Go to market place like odesk or elance
-Search for few professional and check their past works history
-Then check their portfolio and reference if available
-Contact with them
-Give a small task to check their skills and professionalism

Or
Search through search engine like google and yahoo with the desired keywords
check their website and blogs
check their social media activities
contact with them and place a video call to get more idea about the professional

Note: Make a list of question you are going to ask before calling.

Source(s)

4 Years professional inbound marketing experience

I agree with the above, it is simply a case of doing an SEO related search in Google, focusing on your city. Don't however just go for the first one you see, do a little investigation. How well is their own website structured? Do they have a blog? Is it well written?

Also, don't be afraid to ask for an Audit, most companies offer them for free and will go through every detail with you to determine just what your site needs and what the potential ROI is.

I've popped a link below to an official SEO page on my company website, it should give you an idicator into the kinds of things that people should be offering etc. Hope it helps

Source(s)

www.uc4.co.uk/seo-birmingham.asp

It is very simple search professional SEO but when choosing professional SEO services we must check whether they are providing quality services and having high PR.