How can I make sure my will is found?

Writing down your last wishes is one thing; making sure they are found (and therefore carried out) is another.

Although you are under no obligation to have your will registered, it seems wise to do so to make sure it can easily be retrieved upon your death.
Otherwise, it will depend on your loved ones' ability to locate the will wherever you kept it, and to actually pass it on to the notaire in charge of the estate.

If you entrust your will to your notaire, they will ensure it is kept safe by depositing it in the notarial office's safe.
They will also register it with the Fichier Central des Dispositions de Dernières Volontés, a national register of last wishes created by the notarial profession in 1971.

This register is consulted each time an estate is opened with a French notaire.

It gathers information on wills and any other document worth finding upon a person's death: gifts between spouses, beneficiary clauses of life insurance policies, Dutreil commitments...

In addition, the registers of last wishes of Germany, Austria, Belgium, Bulgaria, Estonia, France, Greece, Hungary, Latvia, Luxembourg, the Netherlands, Poland, Romania, Slovakia and Saint Petersburg are interconnected, allowing any European citizen to discover the testamentary provisions left by a deceased person, whichever of these countries the provision was registered in.