People generally think of police officers as being in a position of power that cannot be questioned, and this outlook makes it very intimidating when they knock on your door. You may assume you have to do what they say or that you have to let them in.
You do not. If they do not have a warrant, they may ask for consent to enter the home, but you do not have to give it to them. The only way they can come in against your wishes is with a warrant. If they tell you that they have one, ask to see it before you open the door.
What should you do instead? Some choose to go out a back door, walk around and talk to them outside the house. This way, they can’t claim that they saw something incriminating in plain sight and force a search. Others choose to open the door a crack, perhaps with the chain lock still connected, and talk to the officers without letting them in. You can also talk through the door or through a nearby window.
In some cases, you may just choose to ignore them. If you didn’t call the police and you don’t need assistance from them, you don’t even have to interact with them. Just as you’d ignore an unwanted door-to-door salesman, you don’t have to speak to the police.
If you do get arrested, it’s important to know what privacy rights you have and how a potential violation of those rights could lead to legal action on your part.