When we say the first (main) line of the Shema some congregants cover their eyes to facilitate concentrating more fully on the words. (The Shema is found on page 155 in Siddur Lev Shalem.)
Then, in the third of the following paragraphs, where we read the word “tzitzit,” many kiss the tzitzit of their tallit at each mention, to reaffirm the connection and the commitment implied therein. Tzitzit are the fringes on the corners of a tallit, and are described in these very paragraphs.
There also are two more times when some kiss their tzitzit: after the word “emet,” which bridges two paragraphs, and once after that, at “ledor vador.”
Some hold their tzitzit close to their hearts during the Shema, and some look at the tzitzit throughout.
And what is that buzzing sound, you ask? During the few lines just before “Emet,” some feel it important to emphasize the zayin in “L’ma’an tizkeru va’asitem...” in order to ensure that the meaning is understood, as a mispronunciation could sound like tiskeru (reward) or tishkaru (drunken).
Of course, the most important part is the commitment itself.