Not sure if OK to mention this hear, but the TOPSEOS .com website features the best agencies based on their skills. Simply select USA, Australia, UK etc from the top of the menu, depending on your desired traffic, and then click View Rankings. From there, you can choose from a number of categories, ie. Link Building, Social Media Marketing, Local SEO etc.. and see the top rated agencies. Compile a list and contact them, telling them exactly what you expect from them.
After that, you can make an informed decision if any of these agencies meet your criteria.