In what instances may you need to use the subjunctive mood in French, and how is it formed?

The subjunctive mood in French is most commonly used following specific conjunctions and phrases that express opinion, doubt, or emotion - eg. pour que, bien que, pourvu que, je ne pense pas que, je craint que, etc. The subjunctive mood in the present tense is fairly easy to form, although of course there as some irregularities which must be learnt by heart. However, regular verbs form from the third person plural present indicative form (such as finissent), removing the ending (finiss-), and applying the appropriate subjunctive ending (eg. tu finissES).