This is quite a difficult tense to use , but will give you extra marks if you use it fluently in your exams along with the other more regularly used tenses.
It is to be used when the sentence you are using contains actions or ideas that are uncertain, or subjective (eg your opinion or your wants (these are subjectives notion), when talking about different possibilities, or when you are doubting something.
I think of sentences in the subjunctive as having 2 parts - the start/intro of the sentence (which sets the subjunctive mood) and the next part of the sentence in which the verb used must agree with this mood, by being put into its subjunctive form.
At A-Level, it will be useful to find two or three key sentences which you can use interchangeably, when talking about different subjects, that use the subjunctive (instead of learning all the possible subjunctives and their potential uses!)
3 useful examples of starts of sentences that suggest a subjunctive mood are:
Il faut que - it is necessary that..
Je doute que - I doubt that..
J'apprecie que - I appreciate that..
For example, this is how to use "il faut que" as mentioned above - this can be the first of your multi-purpose sentences that you can slip into any exam:
"Il faut que le gouvernement fasse plus pour aider les sans-abris à Paris" translated means "It is necessary that the government does more to help the homeless in Paris"
Here, the verb "faire" has been put into it subjunctive il form, following the use of "il faut que".
Equally if you wanted to change the sentence to be talking about something completely different such as, lets say, your teachers and what they should be doing, you could easily do so, as follows:
"il faut que notre professeur soit moins stricte" translated means "it is necessary that our teacher is less strict". Here, the word "soit" takes the subjunctive "il" form of être.
You try and put the following english phrase into the subjunctive:
I doubt that England are the best football team in the world
Je doute que...
and also try:
I doubt that Francois Holland likes his job
and now, you make up your own with the next example:
*** here is a link to a page listing subjunctive conjugations of lots of verbs - use this to translate our examples (some of which are the same as the normal present tense conjugations! yay!) and also, choose 3, as I said, and learn them well so you can use these phrases interchangeably in your exam answers!
If you have any questions or need any help, just ask.