Claimants seeking Social Security benefits should hire an attorney after they get denied. Most people can and should file the initial application for benefits on their own.
If denied initially its ok to file the Request for Reconsideration yourself. Most of the work done on your case at this level will be by DDS, and some times there is not much for a lawyer to do.
Once denied at the recon level, it is definitely time to hire a lawyer. The lawyer will get the case ready for the ALJ hearing. Most cases are won or lost at this point.
In most cases, I recommend hiring an attorney after any denial. Remember that most all denials must be appealed within 60 days, or you start all over again.
Even if you appeal your first denial, hire a lawyer to get ready for the ALJ hearing.
After the ALJ hearing it may be more difficult to hire a lawyer, and the case may be too far gone for a lawyer to help.
When in doubt, hire a lawyer the day you get a denial letter. Hire a local lawyer and meet him or her at their office and file an appeal with your lawyer.