If the cops want to talk to you, they will knock on your door.

Chances are it is a neighbor complaint.

If you are suspected in a crime, detectives will show up to question you. If you are considered dangerous, uniform officers will be there for backup.

If they have adequate and reliable information of a crime taking place in your house (like having a grow house) they will get a search warrant. They could get a no knock warrant if they feared the evidence could be quickly destroyed. They will also likely turn off your water a couple of hours before hand. Enough time for the toilet to get used once! Then when the battering ram flattens your front door and SWAT orders you to the ground, you'll have some inkling of how serious it is.

If there is a warrant for your arrest and it is minor, they will stop by a couple of times and knock. Often they just put it in the system and wait for you to be stopped or picked up for something else.

An attorney can find out if there is a warrant for your arrest. The police or da/sa will NOT tell you.