How to analyse drop in conversion – effective & quick

This is a frequent scenario in life of a product manager of a start up or data analyst to figure out why the conversion has dropped all of a sudden of the product they are owning. I have seen a lot of product managers dreading this scenario only because they are not sure where to begin from as they feel this exercise will overwhelm them. To be honest this isn’t that difficult, you just need to check a few data cuts which can be done under 15-20 mins in most of the scenarios (especially when the conversion drop is sudden).