Good news if you hate red tape! When it comes to bureaucracy, it's a piece of cake to plan a trip to Argentina.
French, Belgian, Swiss and Canadian citizens only need a passport to travel to Argentina. This passport should expire, at the earliest, 6 months after your departure from Argentina You don't need a visa unless you plan on staying more than 3 months. So there's nothing to worry about.
No specific vaccinations are required to enter Argentina. Just make sure you're up-to-date with your vaccines. It is, however, advisable to get a shot to protect against yellow fever. Although it's been eradicated in the country, a serious epidemic hit in 2008. If you want to be extra cautious, it'd be a good idea to get shots for typhoid and hepatitis A as well.
You should also think about signing up for travel insurance before your departure. This advice applies to all countries but is even more important if you plan, for example, to go hiking in the Andes.
Dreaming of renting a car or bike and making the trip down the mythical Ruta 40 to Ushuaia? You should probably go down to your local prefecture and apply for an international drivers' licence. It's free and some companies require it for car rentals.
So time has passed, the end of your three-month stay is approaching and you really have no desire to go back. The first thing you could do is go to the closest office of the National Department of Migration and get a supplementary 3-month visa at a cost of €20. Another solution is to just carry on normally and pay the associated fine of €10 when you're leaving the country. And finally, the third solution- which is not only free, but also an opportunity to broaden your horizons: make a quick trip to one of Argentina's bordering countries. Chile, Uruguay, Brazil, Paraguay, Bolivia... the only problem is which one to choose. Spend a day, then go back to Argentina and you'll automatically receive supplementary clearance to spend 3 more months in the Argentinian sun.