I can only say what worked for me, but for what it's worth, here' s my foolproof plan for becoming a church Latin dilettante like me:
1. Obtain and work through A Primer of Ecclesiastical Latin by John F. Collins. It's in an easy format and is pointed squarely toward the student who needs Latin for specifically Catholic purposes. You've probably had some Latin before, enabling you to start quickly and feel very encouraged.
2. Practice regularly. There are at least two simple practices I have found for this:
a. Read. You can read whatever you like, but the Sacred Scriptures is a classic choice. You can get a "Nova Vulgata" Bible from the Libreria Editrice Vaticana, or just get it from the Holy See's website. You can also get an old school Vulgate from the Deutsche Bibelgesellschaft. If you read scholastic theology you will want the latter; if you try to check their citations in a modern Bible you will sometimes end up very confused.
b. Pray. If you are ordained or are aspiring to Orders, you are supposed to pray the Liturgy of the Hours anyway. So why not order typical edition, Latin breviaries? I know they're not cheap, but you won't be disappointed. Get the so-called "economical" edition and put a protective cover on it. Even if you don't know much Latin, you have at least said Night Prayer or the Sunday Week I psalms a zillion times and you will know what it says already.
If you are a priest, think about learning the secret prayers of the Mass in Latin. It's in the back of the Sacramentary, in case you never noticed. If you're interested, I have made an "altar card" of these prayers that I can send you if you want.