I would say that one critical step of the French Revolution would have to be the Reign of Terror.  I think that this would be something that has to be addressed in describing the growth and emergence of the Revolution.  Dickens describes how the Committee for Public Safety members would do a specific dance to signify the start of the public executions, and how Madame Defarge would react to the spraying of blood from the guillotine.  I would say that these aspects should be part of your description of the emergence of the Revolution.  This could be a nice contrast to the spirit of the Revolution that imitated it.  The spirit of equality and transformation of what is into what could be became bookended with a fairly horrific display of public disorder and rule by individuals whose inauthentic motives were shrouded by the most beautiful of poetics.

The French Revolution began in June 1789 with the Third Estate's members convening in what has come to be known as The Tennis Court Oath, a pledge signed by them that would effect a new constitution.  This oath, which was a revolutionary act, was an assertion that political power derived from the people and not from the monarchy.  The oath signified the first time that French citizens were in opposition to the monarchy.

The second event of the burgeoning revolution is the march to and attack on the Bastille in July, 14, 1789.  Since the old prison held only seven prisoners [Dr. Manette is one], the attack was more figurative than literal.  It signified the end of royal authority and most prisoners in the Bastille were political ones.  After this storming of the Bastille, the Declaration of the Rights of Man was written.  After some conflict between liberal assemblies and a conservative monarchy intent, a republic was proclaimed in 1792. 

Monsieur and Madame DeFarge participate in the march upon the Bastille. In Book the Second, Chapter 21, Madame DeFarge is in

...the howling universe of passion and contention that seemed to encompass....

When an old grim officer falls dead, Madame DeFarge  becomes "suddenly animated" and, placing her foot upon his neck, and with her"cruel knife--long ready--hewed off his head":

Saint Antoine's blood was up, and the blood of tyranny and domination by the iron hand was down--down on the steps of the Hotel de Ville....