Well done search engine optimization often called SEO for short, is intended to allow websites to appear in search results when people search for products and services instead of simply company titles. The point is that people searching for things online can obtain a business website with no prior knowledge of the company or its name. You will find all manner of tricks and techniques that fall under Phoenix SEO, but the fantastic sustainable approaches (also sometimes called "white hat SEO") are based around the notion of creating your site easier for the search engine to read and comprehend, meaning they rank you higher in searches for suitably relevant terms.
It's not unusual to opt to outsource SEO to outside advertising and marketing services and other companies, but there are far too many different kinds out there who prefer to take businesses seeking SEO - especially local and smaller companies - for a very expensive ride.
It's truly incredibly easy to discover a decent search engine optimization agency online. Visit a search engine such as Google or Bing and type in "SEO agency." Ignoring the paid ads on top, whichever company has landed on top of the search results are what you need - they need to be quite good at SEO, or their site would not be so high in the organic listings!
To narrow things down a little, you could try expanding your search. Say you live in Essex and need a local service - just type in "SEO service Essex." This can be a terrific way to find market SEO agencies that have specialist expertise in your area.
Occasionally SEO agencies (or at least individuals claiming to be SEO bureaus) attempt to solicit businesses by sending them emails or submitting contact forms with several enticements and offers. But if you see something like this come in then it's better to ignore it if a company which allegedly specialises in search engine optimization is reduced to spamming inboxes to acquire business instead of, say, doing SEO so their site ranks highly and people may locate them anyway, it is likely that they are not very good. The same is true of search engine optimization services advertised on paid advertisements at the top of search engines or banner ads on other sites. If their search advertising isn't any good, why do they have to pay for their placements?
Another thing to keep in mind would be to steer well clear of any search engine optimization agency which promises you "top ranking for x keywords" or something similar. Nearly all modern search engines utilized personalized searching, meaning that everybody sees sites in slightly different position positions based on their personal search history. Modern SEO will use sustainable "white hat" techniques to be able to bring useful traffic to your site, not use exploits and dodgy tips, which will always have them slapped by search engine upgrades such as Google's notorious Panda and Penguin algorithm changes.