A slight bow of the head whenever the name of Jesus is spoken.
When the name of Jesus is said or sung, incline the head. It is small. A stranger beside you may not notice.
At Mass this happens often in the Gloria, at "Lord Jesus Christ, Only Begotten Son" and again at "you alone are the Most High, Jesus Christ".
The same head bow is given at the name of Mary, at the name of the saint of the day, and at the name of the Pope.
Carry it outside of Mass. It is a quiet answer when the name is used badly in conversation.
A name is not a label in Scripture, it is a presence. To speak the name of Jesus is to bring the person near, which is why the name has been the whole content of prayers as short as the Jesus Prayer. The head goes down for the same reason a knee does at the tabernacle: something is actually happening.
The practice comes straight out of Scripture. Saint Paul tells the Philippians that at the name of Jesus every knee should bend, in heaven and on earth and under the earth.
The Second Council of Lyons in 1274 asked explicitly that the faithful bow the head at the holy name, and it has been part of the ordinary courtesy of Catholic worship since.
The Roman Missal still names the four moments: the name of Jesus, of the Blessed Virgin, of the saint being honored that day, and of the Pope.
Nothing obliges you. It is a custom the Church encourages rather than commands, and it is easy to start today without telling anyone.