Often it is believed that a sponsor is only an honorific designation.  In reality, the sponsor assumes the role of journeying with the candidate in Faith before and after Confirmation. This includes praying for (and hopefully with) the candidate as they prepare, being open to answering questions about the Faith, and providing an example of how to live the Christian life.  It is also encouraged that they “follow along” with the program with the candidate and seek to have conversations with them about it.
The Diocese of London strongly recommends that students choose their Godparents as their sponsors to show the unity between the sacrament of baptism and confirmation.  Students need only one Catholic sponsor but may have two so long as they are of differing sex.

Sponsors (according to Cannon law) must:

a) Be at least 16 years old
b) Have received all the Catholic sacraments of initiation. (Baptism, Eucharist, Confirmation)
c) Be a practicing Catholic in good standing (attending Mass weekly, living a life of Faith etc…)
d) Not be the parents of those to be confirmed
e) Be willing to take on the role and responsibility of being a sponsor
Some students have a Catholic Godparent and a non-Catholic Christian Witness as godparents.  Both can attend the liturgy but they must have at least one Catholic Godparent.
If a chosen sponsor lives too far away or is otherwise unable to attend the Confirmation Liturgy, a proxy may be chosen.  Since this person is standing in for the Catholic Godparent and not assuming the role themselves, they need not be Catholic.