When should I use the subjunctive?

The subjunctive isn't a tense (like the present, past or conditional), it's a mood used to express thoughts, possibility or necessity. The subjunctive is triggered by certain verb structures that you will need to recognise. Some common examples include: 1) bien queJ'adore Paris, bien qu'elle soit si chère (I love Paris, although it is so expensive) (trigger) (subjunctive) This is an example of a clause expressing possibility triggering the use of the subjunctive. 2) ne penser pas (to not think) Je ne pense pas que tu aies raison (I don't think that you are right) (trigger) (subjunctive)This is an example of a clause expressing thoughts triggering the subjunctive. 3) il faut que (it is necessary that) Il faut que je fasse mes devoirs ce soir (I have to do my homework tonight) This is an example of a clause expressing necessity triggering the subjunctive.