Right way to teaching Dhamma

Buddha said that there is a specific way to teach the dhamma. That for example, if I remember correctly, among other things, it's important to mention the cause and effect in one's teaching. I can't find this anywhere, can someone give me a source for this? Also, what if I teach the dhamma in a wrong way? Is this causing demerit/bad merit/bad karma? What if I mean to teach it in a right way, but it comes out wrong or even causes the listener to have a strong aversion to buddhism/listening to the dhamma?