The first thing to bear in mind when teaching the subjunctive is not to give the impression that it is difficult. And anyway, as anyone who has watched kids at football training knows, it's the fancy stuff they want to spend time on, not the basics. So the subjunctive is not there to trip you up. It's there to make you look good. And enable you to say things you want to be able to say, as part of your repertoire for extending answers into coherent narratives.
You could teach pupils a list of expressions to memorise which take the subjunctive. I prefer to start with understanding the concept. The easiest way to do this is to look at the word "subjunctive". Pupils can immediately see that it splits into sub and junctive. And they recognise that the junctive is to do with joining or junctions. And that sub is linked to making something less important.
This makes sense as soon as they see sentences where two ideas are joined, and one of them is too SHOUTY and needs subduing.
For example:
I don't think that THE SUBJUNCTIVE IS HARD
In this sentence you can see the two clauses linked by the word "that". And the second clause is shouting very loudly exactly the opposite of what we are trying to say. As I stated at the top, we are not to go around stating that the subjunctive is hard, and the example sentence is trying to make the point that this is not what we believe.
In English the second clause clashes horribly with the overall point of the sentence. Luckily in French and Spanish we can use the subjunctive to smooth over the joining of the 2 clauses and subdue the shouty part. Exactly as the word "subjunctive" promised us.
I don't think that the subjunctive be difficult
No creo que el subjuntivo sea difícil
Je ne crois pas que le subjonctif soit difficile
And from there, we can extrapolate to any expressions which are counterfactual, doubtful, improbable or supposition. We can give pupils a list of examples, let them see it in context, and add it to their repertoire.
Another example would be the sentence:
I am sorry that YOUR DOG'S DEAD.
Again, the second clause is insensitively shouty and drowns out the overall message. We use the subjunctive to tone down the shoutiness of the clause. And by extrapolation all value judgements and emotions, both positive and negative.
The other use of the subjunctive is again one where English phrasing can lead to bizarre unintended implications.
My parents don't want me... to be a dentist
I want you... to do well in your exams
These sentences start off in an alarming way that we can avoid by using the subjunctive.
My parents don't want that I be a dentist
Mis padres no quieren que sea dentista
Mes parents ne veulent pas que je sois dentiste
That's much better! Thank goodness for the subjunctive. And by extension, we can teach pupils to use the subjunctive for whenever you are getting someone else to do something.
I am not advocating rote learning fancy expressions to impress the examiner. We had enough of that with the old GCSE that destroyed language learning. I am teaching pupils to understand how to use the subjunctive to create meaning. And they integrate it into their repertoire of giving opinions, justifying them, and narrating events with differences of opinion, what people said, what was happening, and what happened. (Explained in detail in the video in this post.)
In particular the "my parents don't want" use is easily included in the pupils' repertoire. Maybe with topic like jobs and careers, but also in any answer about going out with friends.
Me encanta salir con mis amigos, pero mi madre no quiere que vuelva tarde, por ejemplo el fin de semana pasado fui a la casa de un amigo y...
If you want to see exactly how I talk about this with pupils, then I have this video on the subjunctive for French and Spanish. Includes free bongo solo.