Listen to the Ordinary of the Mass in Latin and practice on your own:
(Broadband recommended)

Asperges me

Kyrie

Gloria

Prayer of the Faithful Response

Preface dialog

Credo

Sanctus

Mysterium Fidei

Pater Noster

Agnus Dei

 For music rehearsal:

Cyberhymnal

Communio

Partituras Corales (Choral Parts)

Musica Sacra

CPDL.org

On the selection of music for the Mass:

Sing to the Lord

Jubilate Deo

Sacrosanctum Concilium (Paragraph 22)

Code of Canon Law (Can.  846 §1)

General Instructions of the Roman Missal (ch.1, #24)

Redemptionis Sacramentum (#s 57-59)