How do I find out what is liturgically correct in Mass?
There are two fundamental resources that guide the celebration of Mass: the Roman Missal itself, particularly the “Order of Mass,” which is normally also included in daily Mass Missals; and the General Instruction of the Roman Missal (GIRM).
There are optional prayers and readings, depending on the time of the liturgical year, so don’t presume related differences are actually incorrect, as your daily Mass missal will not be as exhaustive as the Roman Missal. In addition, if you do see something problematic, approach your priest, and most likely you can work things out at the parish level. If necessary, one can also bring liturgical needs to the diocesan deanery level, the diocesan bishop, and, if sincerely desired, the Holy See.