The  (Portrait) mode blurs the background to make the human subject stand out. It also makes skin tones and hair look softer.
Select the location where the distance between the subject and the background is the farthest.
The further the distance between the subject and background, the more blurred the background will look. The subject will also stand out better against an uncluttered dark background.
Use a telephoto lens.
If you have a zoom lens, use the telephoto end to fill the frame with the subject from the waist up.
Focus on the face.
As you focus before shooting, make sure that an AF point is displayed on the face (in viewfinder shooting), or that the AF point on the face is green (in Live View shooting). When shooting close-ups of the face in Live View shooting, you can set [: Eye Detection AF] to [Enable] to shoot with the subject's eyes in focus.
The default setting is  (Low speed continuous). If you keep holding down the shutter button, you can shoot continuously to capture changes in the subject's facial expression and pose.