Paying attention to the reading:
One is to have a Chumash open in front of him and follow the reading during Kerias Hatorah. Some are accustomed to read along silently with the Baal Korei to help them concentrate. Others, however, rule that one is to remain silent, and read along in his mind.
 Sefer Haminhagim p. 30 [English]
 M”A 146; M”B 146:15