Here are some close up images I have taken with my phone. A good close up picture contains a sharp subject in the foreground and the background blurred out of focus.
1) This is a sharpener i have placed on the right side of the frame, the
screw and the blade are in focus and the background is blurred out of
focus. 
2) This is a close up of wires in the server and a few Ethernet ports.
All these lines present in this image make it very effective
2) This old keyboard unusually has a Euro (€) key. This interested me so I took a picture of it. I kept the one key in focus and the other end of the keyboard is blurred out.
4)
Mac Keyboard. Very similar to image [2], this is a close up of a mac
keyboard. The "L" is in focus and the letters at the other end of the
keyboard (c, d and f) are blurred out.
5) This is an image of a audio socket. This image is different to the other close ups, this image has the focus more in the middle of the frame as appose to the foreground. The background, as well as the foreground are out of focus.
