The subjunctive is a tricky part of the french language, one that often confuses students.
There are several cases in which it is used:
- when you express a desire, a will, an order (e.g. Je veux que tu...). But NOT after espérer
- when you have to do something, so for example express something with the phrase "il faut que"
- To express a possibility, uncertainty or doubt (e.g. Je ne suis pas sure..., c'est possible que...)
- after certain impersonal expressions (e.g. Il est important que..., il est logique que..., il est possible que...)
- after certain conjunctions (e.g. pour que, afin que)
- to express a negated opinion (e.g. je ne crois pas que + Subjonctif, BUT Je crois que + Indicatif, je ne trouve pas que + subjonctif, BUT je trouve que + Indicatif)