^This.
Also:
Knock or ring the doorbell;
Ask permission to enter;
If you have a warrant, show it and permit the citizen to read it;
If the dog is on a chain, don't shoot it;
If the dog isn't on a chain or otherwise secured, offer the citizen the opportunity to secure it before you think of shooting it;
Once inside, don't deliberately wreck the place while conducting the search;
If you think the coke's in the couch cushions, let your K-9 partner take a whiff before cutting them open;
If you don't find what you're looking for, help the citizen put back anyting you moved, apologize, and leave;
And last but not least,
Diouble-check to make sure you got the right house before knocking.
In this way, shootings of and by police will be greatly reduced.