As an Altar Server, you should know everything you have to do during a Mass or even before and after a Mass. You should know that everything in the Mass is Holy and you are part of it, so, you should also act Holy not just in the Mass, but also outside the church, in your community to be specific.
In this page, I will tell you everything I know as an Altar Server. First in Preparation. When you arrive at the Church or at the Sacristy, don't just passed by the Presiding Priest without showing any respect. You should greet him or blessed in his hands as a sign of respect. Also, wear clean clothes and shoes, and try to wear black shoes as possible. And for the ladies, have your hair tied back. Don't make it look like that you have just woken up from sleep. Be conservative as possible. And before the Mass started, discuss with your co-servers what you should do during the Mass. That way, there will be no more argumentation will happen when the Mass started. It will also help you r group to serve smoothly. Make sure to lit 2 candles for Daily Masses and Six or more for Sunday Masses.
Next is the Procession, in Sunday Mass, Processional Cross/Crucifix and 2 Processional Candles are needed during the procession. Make sure to hold the Crucifix properly, hold it with both hands, Right over Left at chest height. And when you Genuflect, make sure you put your right knee to the floor. But if you are Carrying something, just do a simple bow. And Remember, it is a Holy Mass, Christ is present during that time. Don't think as a server that it is just a chore, do it heartily. Don't stand like you're just in your house, you should have your shoulders back, stomach in, head forward, and hands together. Whether you are walking, standing or kneeling.
The third one is the Opening and Closing Prayer. If it is your duty to bear the Sacramentary, the priest usually read at the red ribbon.If you are shorter than the priest,hold it with ribbons down and place the book beneath your neck, but if you are taller than the priest, hold it to your left side with your right arm. When sitting down, don't just sit down like you are watching a TV in your house, do it with grace and with full respect, sit with sync with your co-servers, with proper posture and hands on your knees.
This video shows how to serve PROPERLY in a Holy Mass. If you are willing to know how to serve at the Altar, well, this is the right video for you.