How to take a photo with a small depth of field (clear theme and blurred background)?

DC is DC after all? Because I have never used telephoto DC myself, I can only talk about the method of ordinary DC? If there are instructions, try to turn up the aperture as much as possible? But the effect is not great. The most important thing is to close the distance between the lens and the subject, keep the subject away from the background, and the most important thing is to turn on the macro? Send a film I shot with a few hundred dollars of junk DC.