For the input half of maintaining solvency, Congress needs to leave whatever money is placed into the system alone. It should only be used for Social Security. No more dipping into the pot to fund pet projects! Congress should be required to asses the current value of the Dollars removed from the fund over time. That money (or at least a reasonable portion of what was removed) should be returned with interest (Treated as a National Debt) as indexed to the Cost of living indices. Everyone working in this country should be required to pay into the system. A consumption model such as the FairTax may be the only way of ensuring solvency of the Social Security Program (and pay off our national debt as far as that goes).
The consumption side of maintaining solvency is to eliminate the waste, Fraud, and Abuse. Any fines and penalties assessed on those that have abused the system, needs to be placed into the Social Security Fund and not the General Fund. Finally, administration costs need to be controlled.