Fortunately the human brain seems to be made in such a way that it can pick up systems from a most unsystematic presentation which means that most students get there in the end. However a systematic presentation will make it a lot easier for both teacher and student and a lot faster and therefore more economical for everyone.
The basic process which can be adapted to all tenses is to teach, in 5 steps:
(In groups this can be done while doing step 3 if the teacher is careful to set the model for the question.)
The fact that questions can not be used straight away means that a transfer technique is required. That is to say that the student must be in "repeat" mode, and at first simply repeats the teachers examples, enriched sometimes, by replacement drills.
The exact application depends on the tense. Sometimes only one person of the verb can be taught at a time. "I am" is a good example. None of the other persons of the verb use "am" so it has to be covered all on its own, affirmative and negative, as does "you are", before a question can be asked.
In the case of the simple present (taking the verb "to go" as an example) there are two basic forms, "go" and "goes" and these must be separated - in fact with this word there is a good case for doing the third person first as students seem to have less difficulty knocking off a learnt "s" for the third person than remembering to put it on. However the fact that all persons other than the third are the same means that I, You, We and They can all be taught together.
The importance of contrasts between tenses in their introduction.
Unless the new tense is introduced in a context which demonstrates the need for the tense, students will tend to be slow to absorb the information and even, in a curious way, to resent it as an unecessary complication. I suppose a classic example of this would be learning the subjunctive in French. It just doesn't seem to be necessary to the student who falls upon it for the first time. Of course the subjunctive exists in English too and on those rare occasions when the teacher wants to point it out a good approach is to say "What's the difference between 'God save the Queen.' and 'God saves the Queen.'. You don't really want a coherent answer to the question, (you might well be hard put to formulate one yourself on the spur of the moment) but a moments reflection will usually make it clear to a student that there is one. Once he is pursuaded of this he will learn more efficiently.
This example I have given is maybe not the most useful in terms of practical teaching but it does illustrate the point that a tense should be contrasted with that, or those, with which a student is most likely to confuse it. Some of these are obvious: when you introduce the past for the first time, probably with the verb "to be", "was" is contrasted to "is" as a starting point and, if necessary, "were" to "are". Others may be less evident and here are some tenses which should be contrasted with each other, not only when the second of them is introduced but as revision.