How do I know when to cross myself during Mass (Novus Ordo)?

I've been going to Catholic (Latin Rite) Mass my whole life and am constantly surprised by the different times that people will cross themselves during the Liturgy. I only do it when the Priest says the "Father, Son and Holy Spirit" (and I try to hang on to Holy....Spirit for as long as it takes for him to finish the sentence (not sure if that's necessary). And doing the three crosses before the Gospel is read (which wasn't certain is _in_ the rubrics but [asked about here](https://christianity.stackexchange.com/questions/50229/why-do-catholic-laity-cross-themselves-three-times-before-the-gospel-is-read) and found it to be) I've seen people cross themselves during the Penitential Rite, the Kyrie, and at other times during the Eucharistic Prayer. And crossing themselves at a Mass with the Bishop when he comes down the aisle blessing everyone (regardless of whether he has holy water). Is that just how we _catch_ his blessing? People also cross themselves after receiving communion, but as a Catechist, I was taught this is not right, so I'm not asking about that. [see this question](https://christianity.stackexchange.com/questions/36625/why-do-catholics-make-the-sign-of-the-cross-at-the-eucharist) I'll probably ask a follow up about crossing thyself during the Liturgy of the Hours, so no need to include that in the answer.