I would look for the designations that require a broad and deep commitment to education, a rigorous test for competence, and strict requirements for ethics and continuing education. Among these are: CFP (Certified Financial Planner professional), ChFC (Chartered Financial Consultant) usually attained by insurance professionals, and PFS (Personal Financial Specialist) available to CPAs through the AICPA. CFA (Chartered Financial Analyst) is perhaps the most rigorous designation and focuses on investment analysis and portfolio management skills, not financial planning.
As a clarification, CPA's are held to the fiduciary standard at all times. On the other hand, CFP's are NOT always required to be fiduciaries. From the CFP's Board of Profession Conduct: "When the certificant provides financial planning or material elements of financial planning, the certificant owes to the client the duty of care of a fiduciary as defined by CFP Board. " So when the advisor is simply selling securities (which is not necessarily considered financial planning), the fiduciary standard does not apply to them, thereby allowing them to collect commissions on sales of financial products. I hope this helps to clarify the distinction between these designations.
One of the most respected sources of education is the American College www.theamericancollege.edu and it provides clear details on the designations CFP, ChFC, CLU, CAP and other programs. I am by nature more bias to my choice of ChFC over the CFP. I went through 10 courses of which 6 of these were the same materials of the CFP. The CFP is comprehensive cram course rather than ChFC with 10 separate exams each 2+ hours and 150 detailed questions. I wanted to learn and apply deeply more materials and more testing and work over a longer period of time.
I would like to expand upon on a few points made in other posts.
First, CFA charter holders are required to develop proficiency in financial planning in addition to investment analysis and portfolio management. A significant block of the curriculum focuses on the role of planning (determining client needs and goals, constraints, special circumstances, etc.) in the investment management process. It would be inaccurate to imply that because the CFA program includes other program areas, that it is not appropriate or does not adequately train an advisor who is engaged in financial planning in their advisory practice. Take a look at the Private Wealth Management section of the CFA Institute Website (http://cfainstitute.org/learning/topics/Pages/privatewealth.aspx) and you will appreciate the breadth and depth of topics and issues that are covered.
Second, the term "fiduciary" may not tell you everything you should know about how an advisor works with clients. As Victor points out, an advisor may both claim to be a fiduciary (as all investment advisor representatives have a fiduciary obligation by law) and accept commission-based compensation as a registered representative of a broker-dealer. In my view, this anomaly is indicative of a flawed regulatory system and it highlights two critical questions that you should ask of your prospective advisor: (1) how do you determine which investments to recommend to your clients, and (2) how are you compensated? If the advisor starts to squirm, look elsewhere for impartial advice.
Finally, there is an excellent brochure titled "Cutting Through the Confusion: Where to Turn for Help With Your Investments." It is produced by the Coalition on Investor Education, whose members include the Consumer Federation of America, the North American Securities Administrators Association, the Investment Adviser Association, the Financial Planning Association, and the CFA Institute. I recommend this publication to anyone who wishes to understand the significance of different professional credentials and regulatory registrations. You can download a PDF version of the document at the Consumer Federation of America website (search "Cutting Through the Confusion" and it is the top hit at Google).
As A CFP® I am biased, but like choosing a doctor you need to see what you most need help with. I have always felt that the Certified Financial Planner tm practitioner is like a general practitioner. I often refer my clients to CFA (Chartered Financial Analyst), CLU (Certified Life Underwriters), CPA (Certified Public Accountants), Attorneys, etc because they provide better depth on a subject, but as a CFP® I need to have general knowledge on all subjects and know when and who to refer people to for the best answers to their questions. I wish I was smart enough to know all things, but a designation does not guarantee expertise it only means you have core competence to pass an exam. The experience and how it is applied is what is really important. I would look for an advisor that is comfortable enough with their own skills to refer clients to others when needed.
The most common and highly regarded designations are CFA, CFP, CPA, CLU, and ChFC. All require a different level of education and experience to obtain. The most important question to ask, as highlighted by other's answers, is what type of questions/concerns you are looking to address by working with a planner/advisor. Most professionals tend to specialize in a few areas or develop a niche that they excel at. Designations may help you decipher what niche or specialty that may be.
CIMA is also a useful certification - Certified Investment Management Analyst
According to all objective 3rd parties: CFP, CPA, CFA, RIA are the professional designations that are recognized as being meaningful, and that require some minimum level of education, experience and require upholding of the Fiduciary Standard of Care. Most of the other alphabet soup of designations can be gotten through a 3 hour course online.
CFP is the gold standard. I would further check to ensure your advisor is a FIDUCIARY and Independent so they are not looking to sell you high priced products and services, but rather put your interests before their own.
CFP--Certified Financial Planner for run of the mill financial planning.
RMA--Retirement Management Analyst for full on retirement income planning.