Teaching Grammar

Following the thoughts of Jeremy Harmer, grammar has always been a problem for language for both, teacher and student. He says that rules are always complex and interpretations are often highly controversial. Why is grammar such a problem?
According to Mr JH there are some guidelines for teaching grammar such as by giving the students what they want and need, trying to be sensitive to see some approaches to grammar that can interest students, motivating them by the use of some more attractive activities.
Another point is : Teachers need to know grammar. They have to know what they are talking about when they are asking the student.
Make it easier to talk about it, is another point. It is extremely important to be able to talk about grammar whether discussing problems with colleagues or helping students out with queries and problems . Its important to see that the terminology is used for guidance rather than for imposing rigid rules then everyone will find it usefull.
Another point : Being unafraid to say what you don't know. Grammar is such a large and complex field .It would be unrealistic to expect teachers who are not academic grammarians to carry all information in their heads. Another tip is : To know where to look for the information the teacher or the students need. Sometimes the textbook or our own knowledge will not give us most of the answers we are looking for. There are lots of good grammar books to refer to them frequently.
I agree with Mr. Jeremy Harmer that we need to evaluate each approach to grammar with a hint of scepticism always trying to make it easier to teach and to make, in the methods, the necessary changes.