The Magen Avraham (OC 134:3) writes that the one honoured with hagbah should open up the Sefer Torah enough to display three columns, though the Mishna Berura (134:8) writes that one capable of safely opening it more should do so. The seam connecting the pages should be in the middle (See Shulchan Aruch OC 147:3; Aruch HaShulchan 147:13). When doing hagbah, one should turn clockwise, slowly enough that people can see the letters (Mishna Berura 134:9).
The Shulchan Aruch (OC 134:2) and Rema (Darchei Moshe 147:4) write that when the Torah is lifted, there is a mitzva for everyone to look at it, bow down, and say Vezos habracha..
R’ Tzvi Pesach Frank (Har Tzvi OC:64) writes that he is puzzled as to why people aren’t particular about this halacha, especially as we mention bowing when we take the Sefer Torah out (דסגידנא קמיה in Berich Shemei)!
While many people point with their pinky during hagbah, this is not the ashkenazi custom (See Rivevos Ephraim 5:215).
According to the Gemara (Megilla 32a), the honour of gelilah is equal to all of the other honours. (See Shulchan Aruch OC 147:1). The Mishna Berura (147:5) writes that this applies to the way we do hagbah today, and notes that it is no longer treated this way. The Aruch Hashulchan (OC 147:9) questions the practice of many gabboim who will give gelilah to a young boy. One theory behind this is that the Torah used to be lifted before leining (as is practiced in many sefardic and chassidic communities). Now that gelilah is the last honour, it no longer receives the same prestige.Ramban (Devarim 27:26) writes very strongly about the importance of performing the mitzva of hagbah and gelilah properly. Let us take heed of his words.