Not been to a Chrism mass myself, but what happens when serving is as follows (and remembering I'm not a server):
(I presume you won't be preparing the altar, just serving?)
Give the chalice/paten/corporal/purificator to the Celebrant, and he/she will prepare the altar (or deacon may do this). The ciborium/flagons will either be on a credence table, or will be presented as part of the Offertory. Give the ciborium to the priest/deacon.
Bow
The wine flagon hold in your right, the water in your left, handles out.
Give the wine flagon the the Celebrant, transfer the water flagon to your right, receive the wine flagon back in the left, hand over the water flagon.
Receive water flagon back, bow.
Return to credence table
There may be a money offertory too - will you be receiving this? In which case sidespeople will present you with this, you bow to them, and hold the collection up to the celebrant to bless, before placing it wherever it goes.
Lavabo bowl in left hand, lavabo towel over left wrist, pour water over celebrants fingers, he will then use the lavabo towel to dry fingers
Bow, return to credence table
Thats pretty much it as I recall. Bowing might vary from tradition to tradition, if anyone bows, you bow back is the rule of thumb :o