Take a look at my Austria game in my signature; the strategy I use seems to be working very well.
1. Ally with France, Sweden, Two Sicilies, Switzerland and declare war on Prussia with wargoal Aquire Prussian Wuttermburg. Most likely at least one of them will not decline to aid you.
2. Form SGC
3. Give them saxony, let the Hannover event fire, and let them form NGC then declare war and liberate a nation.
4. Continue doing so (and sphering the liberated nations) until NGC is knocked out of great power status and sphere them.
5. United Germany and then do whatever.
1. Ally with France, Sweden, Two Sicilies, Switzerland and declare war on Prussia with wargoal Aquire Prussian Wuttermburg. Most likely at least one of them will not decline to aid you.
2. Form SGC
3. Give them saxony, let the Hannover event fire, and let them form NGC then declare war and liberate a nation.
4. Continue doing so (and sphering the liberated nations) until NGC is knocked out of great power status and sphere them.
5. United Germany and then do whatever.