Despite the romantic/Hollywood/Gaullist image of the French Resistance blowing up bridges and ambushing German columns, in reality these sorts of paramilitary operations were rare, at least until 1944. Most resistance activities were much less dramatic, if no less important. It was only after D-Day that resistance groups were able to wage open warfare against the Germans in a real capacity.

Resistance was seldom and sporadic in the first year and half of the German occupation, and categorically non-violent. It consisted mostly of individual displays of defiance and contempt for the Germans - daubing a “V for Victory” on a wall, or deliberately working poorly on factory orders bound for Germany. A woman in Paris supposedly went around carrying two bamboo poles – in French, deux gaules, a pun signifying support for Charles de Gaulle.

Over time, underground resistance networks began to coalesce from the most disaffected. These were mostly small groups, independent of one another and politically heterogeneous. For an example of how diverse resistance movements could be, one can compare two major early groups like Henri Frenay's Combat in the south of France, composed of conservative army officers who supported Pétain initially but hated the Germans, and the Paris FTP-MOI (Francs-tireurs et partisans main-d'œuvre immigrée) led by the poet Missak Manouchian and composed of Armenian, Italian, and Eastern European communists and Jews.

Once they had been organized, there was the question of what resistance groups would actually do, which depended on their location, their composition, and their politics. But combat was always the exception rather than the rule. Printing underground newspapers, radioing intelligence to the Allies, and helping downed airmen escape France were more common activities for resistance organizations. A good example of both the work and the risk ran by resistance cells is the Groupe de musée de l'Homme, a network created by a number of academics and the first resistance group in Paris. They printed and distributed an anti-Nazi broadsheet titled Résistance, filtered information to the American embassy in Paris, and helped British soldiers stranded in France after the 1940 campaign to escape. In early 1941 the Germans broke up the group thanks to a Gestapo informer and arrested its members. The men were all shot and the women condemned to slave labor in Germany. Prior to 1944 this was the sort of activity conducted by (and often the fate of) other groups as they sought to build organizations and find ways to hamper the occupation. Some of it was very effective, such as the Comet Line, a very large network of resistors in France and Belgium who saved over 5,000 downed British and American airmen from capture and got them safely back to Allied territory.

When it came to striking back directly against the German war machine, the most common strategy was sabotage. French factories played an important role producing equipment and war material for Germany, and owners and workers who opposed the Germans could hamper their efforts merely by working slowly or poorly on purpose. For example, the chairman of Citroën directed his workers to set the oil indicator of trucks a little higher than it was supposed to be, so that the gauge showed an incorrect amount of oil. When the trucks were sent to the Eastern Front, they would run out of oil unexpectedly and leave German troops stranded. Workers themselves organized resistance, with Lyon being a notable center of blue-collar networks who could harm production through botched orders and strikes. Workers could also supply information to the Allies to make their bombing raids more destructive, although of course this came at a terrible price in civilian lives, since 68,000 French people were killed by Allied bombs in the course of the war.

Additionally, resistance cell conducted sabotage directly against targets like rail lines, mines, communications and radar installations, etc. This avoided the collateral damage caused by air raids, and was often more effective than crude saturation bombing. One notable success was Harry Rée's sabotage of the Peugeot works at Sochaux, which were pumping out parts for German panzer divisions on the Eastern Front. Rée was an Englishman born to an immigrant father and an agent in the Special Operations Executive, the British organization tasked with helping the French Resistance. SOE operatives agents were sent to France, usually dropped in by parachute, with money and equipment to organize sabotage. They were also a political tool for the Allies, since unlike the myriad of squabbling resistance groups, SOE agents were loyal directly to London. Rée linked up with resistors and made contact with workers inside the Peugeot factory, supplying them plastic explosives. The workers used them to blow up the factories turbine compressors and electricity transformers, putting its production lines out of work for months. Rée was particularly pleased because he was a pacifist and worried that an RAF attack would cost hundreds of lives, reflecting that it was "‘a wonderful job for an ex-conscientious objector to stop bombing by blowing up machinery."