i am sorry if i am not understanding your question correctly, but buying a property from an estate is just like buying from anyone else. if there is a probate estate, the executor/administrator signs the contract of sale and acts as the "seller." if there is no estate, all of the "heirs" should sign the contract. either way, from a buyers perspective, the process is the same for this and any other "conventional" purchase transaction.
if you are asking how do you find an estate that is selling a property, or how do you approach / identify an estate sale before the property is offered for sale, i will defer to the realtors, brokers and investors who monitor the questions posed on this list