Lets say the scenario takes place in a house. An easy way out would be to burn the house down (Which I highly recommend if you are in a rural location that isn’t near a road) but your neighbours will snitch. Before committing the crime, you should have proper gloves (not cotton ones) like ones you’d use in the garden so fingerprints aren’t left on it. Make sure to cut off their fingertips, toes, and rip out all of their teeth so they can’t be identified if the body looks unrecognisable. If your using an object like a hammer, drive very far from your home and make a hole under a tree then put it there and cover it up with leaves and twigs. Remember to bury them VERTICALLY. Make sure the hole is very deep but enough so that you can get out of it. Put a animal on top but stab it to death and make it look like a wolf would have murdered it so sniffer dogs don’t track it. Burn your clothes afterwards, as even the tiniest piece of DNA can get you caught. Clean the scene when its still fresh. If its not on carpet, brush it VERY WELL with bleach and other strong cleaning products, again use gloves, like the ones you’d use to wash dishes.

Fun fact, if you inject your target with pure oxygen, it can actually kill them which is cool. The FBI developed a gun which had ice bullets, so when the body melted it, it had something inside it that disguised the cause of death as a heart attack.