See some weird stuff at Mass, and want to know if it’s legit? By “weird stuff,” I mean priests leaving the altar to shake hands during the Sign of Peace, having announcements in the middle of the Mass, or letting a layperson give the homily, etc.? Or a church building with the Tabernacle hidden in a side chapel where you have to look for it? Well, here’s a January 1999 article from This Rock about the Ten Most Common Liturgical Abuses. It cites to the specific canon law and GIRM sections to let you know not only that all the above are illicit, but why (and according to which precise rule).
Also worthwhile: Redemptionis Sacramentum, Cardinal Arinze’s killer instruction on the issue. If everyone followed this, liturgical abuses would be gone. Overnight.