What triggers the subjunctive in Spanish?

When deciding whether you should use the subjunctive, you should first consider if there is an element of doubt, uncertainity or desire in the sentence. If so, it is likely that the subjunctive should be used. E.g I don't think that we will leave late > No creo que salgamos tarde. Here, the uncertainity arises from the fact that the speaker is not sure when they will leave. Therefore the verb 'salir' must be conjugated in the subjunctive. Another tip for spotting a subjunctive trigger is the use of 'que' in a sentence you think might need the subjunctive, as triggers often include 'que'. A few examples of this would be 'Es importante que', 'Es bueno que' and 'Es probable que', which all trigger the subjunctive.