How do I form a negative construction in French?

In French, a negative is formed with the words "ne" and "pas". These are placed either side of the main verb of the sentence, 'sandwiching' it. For example the sentence "Je sais" - "I know" can be made negative by placing "ne" and "pas" either side of the verb "sais", which results in the sentence "Je ne sais pas", meaning "I don't know".
The same rule applies to sentences that contain more than one verb, such as "J'ai mangé" - "I have eaten", but the first verb needs to be 'sandwiched'. Therefore, we just need to add "ne" and "pas" to "ai", which creates "Je n'ai pas mangé", meaning "I have not eaten".
We can also create other negative meanings using the same 'sandwiching' method but with other pairs of words, such as "ne" and "plus" for "no longer" and "ne" and "guère".