As I am just getting started in RE, I've mostly faced files packed with a single-layer of packing , such as UPX, ASPack, etc.
Unpacking these protections is fully documented online. The problem begins when I deal with multiple layers of packing, especially concerning malware. I have followed some tutorials though they're usually not detailed enough. They seem to go through a tedious process to find the OEP. For example, they start by dealing with common packers (which is the easy part) and then they begin to set breakpoints everywhere "in calls and jumps" and tracing through the file here and there, which is for me the hard part that I have described above. At this point, I have no clue for what they are seeking or for what they are aiming, and then after some work, they find the OEP!
So what logic did they follow in that process? Also, because I know that the subject is broad, I'm also interested in some keywords.