There are many different types of accreditations and designations for residential real estate agents. The most important is that the person you hire be a Realtor (c) which means that they subscribe to the National Association of Realtors' Code of Ethics. Most of the local real estate professionals do carry this designation.
The next question you might consider is whether or not the agent has a sales license or a broker's license. Obtaining a broker's license requires additional education and passing a different licensing test. Some sales licensees choose not to get this designation because it is not their intent to function as a broker. Though a Realtor may not be a broker, this does not mean that they are less effective as a real estate practitioner.
There are many other designations. Here are a few that are commonly seen in our local area:
CRS - Certified Residential Specialist which requires completion of some high level coursework
GRI - Graduate of the Real Estate Institute - also requiring some high level coursework
CIPS - Certified International Property Specialist
e-Pro - a class requiring proficiency on basic computer skills
QSC - Quality Service Certification that emphasizes service, accountability and professionalism
SRES - Senior Real Estate Specialist that includes training on working with clients over the age of 55
There are other designations as well, but these are the ones that are more common in our local area.
The most important consideration is finding someone who will keep your interests paramount and who will serve you with enthusiasm and integrity. If you are looking for a Realtor a good way is to ask your circle of friends and colleagues for a recommendation. You can also check on sites such as Yelp.