How would I find out if someone has made a will prior to death?

Generally you can't (unless it's discussed openly by the person making the will). Because of the amounts of money people can leave and the chicanery people will get up to in order to receive that money, it's generally accepted that even the existence of a will is a private thing (unless discussed by the person making the will).

In my own family, for instance, my great-grandfather had a stipulation in his will that anyone who didn't come to his funeral got nothing (regardless of what the rest of the will said). And this is why we didn't find out about his death until three months after the funeral. His daughter knew the codicil was there and wanted a bigger share of the money.