What are 3 key ideas of the meeting of the Estates General?
The question is a touch vague, but I hope this will come close to what you need. I'm assuming that you're really talking about the meeting of what was called the National Assembly. The Estates General were supposed to meet but they never met as such because of the problems between the 3 estates. Anyway, once they met:
1. Voting in the Assembly would be by individual representative, not by each estate having one vote. This gave more power to the third estate.
2. The first and second estates gave up (8/4/79) their feudal rights -- their power over the lands they had controlled.
3. The Assembly wrote the Declaration of the Rights of Man and Citizen. This was essentially a new constitution along more democratic lines. It also included protections for various rights of the people.