20:3 The shaliach tzibbur should be careful that, when he finishes one blessing, he not start the next until the majority of the minyan has said Amen. If he starts the next blessing too quickly – for example, if he said “Magen Avraham” and immediately continued “Atah gibbur” so that the minyan did not have a chance to respond with Amen – then the blame for the missed “Amens” lies with him.

20:4 During Kedusha, one should stand with his feet together like a single, straight leg as per Ezekiel 1:7, “their legs were like a straight (single) leg.” When saying “kadosh, kadosh, kadosh,” “Baruch kavod,” and “Hashem yimloch,” one raises himself up on his toes. The practice is to look upward; it’s preferable to shut one’s eyes. (There are places where the custom is not to lift oneself up. In such places, one should follow the local practice – Mishna Brurah 125:8.)