The purpose of this post will be to look at one badly neglected reading of Romans 8:29-30. Though a lot can be said about Predestination itself, I think this is a good article that summarizes the Catholic view. For now, I just want to look at these two verses, since I think the details given are often get overlooked because people don't know what to do with them.
29 For those whom he foreknew he also predestined to be conformed to the image of his Son, in order that he might be the firstborn among many brothers. 30 And those whom he predestined he also called, and those whom he called he also justified, and those whom he justified he also glorified.
This passage is often read as referring to man's whole life being predestined, from their conversion ("called") all the way to Heaven ("glorified"). While there is truth to that concept and a legitimate interpretation of this among some of the Fathers, notably St Augustine, there is also an illegitimate interpretation that the reads it in a way that denies free will and that some are predestined to hellfire. (This illegitimate understanding of predestination has been formally condemned by the Church.) But there are other interpretations that are worth noting that don't really see this as predestination 'from start to finish', but rather the "glorious" predestination to adoption.