No matter how much my teachers or textbooks explain the subjunctive mood, I still get it wrong and I don't really understand. Why?

English grammar and Spanish grammar are, relatively, quite similar, so it comes as a shock when we see something totally alien to us, the notorious subjunctive. Put simply, there are some situations, when we're talking about something that isn't a concrete truth, in which we must use the subjunctive. This may be talking about desires, doubts, negative opinions or possibilities. E.g.: puede que no vengan al bar esta noche (they might not come to the bar tonight - possibility/doubt). To form the subjunctive, take the verb you want to change and put it in the present tense with 'yo'. Venir - yo vengo.Then take off the -o. If the verb is an -ir or -er verb, add -a, if it is an -ar verb, add -e. Venga. Now conjugate the verb as normal.But there are seemingly endless exceptions and subtleties. My Spanish teachers couldn't always give me clear answers, so how are you supposed to get it? Simple. Draw up a big table, with 'subjunctive' on the left and 'indicative' on the right. Starting with a few examples, note down the words and expressions that 'trigger' the subjunctive or the indicative. You will constantly add to this and, through revision and practice, memorise all the 'triggers'. Once you give up the need for an explanation for every example, it becomes much easier!