One measure is to collect back taxes. Apparently the Greek government wasn't concerned with tax collection, which is unusual for a government. Other measures include increasing the VAT (Value Added Tax), reducing spending, increasing taxes, and reducing the number of government employees which is one of the highest at over 16 percent. They have also reduced regulations to form businesses, however those pro business measures are terribly inefficient in a bureaucracy built on disincentivizing business growth and development. Public pensions have been frozen and the where it was allowed to retire at 60, now no one can retire at 60.
Attached is a more in-depth analysis of the Greek austerity measures -- which by the way most have not been implemented. In fact the first measures taken back in 2009 have not even been implemented yet.