Most of the rookie photographers make a lot of mistake while focusing the pictures.
If you want your photos to be clear and and well focused you must make sure that the object is well focused.
The background should be blur enough so that there will be difference between object and background.
Never use Photoshop to focus background…Its completely wrong.
Just telliing you that because some of the stupid people do that.
Normally when you focus always try to use totally the facility provided to you by your device.
I mean to say when you look into your view finder you will see a bunch of dots, depending upon the camera you use , i mean dots for Cannon Cameras and Boxes for Nikon Cameras.
Those Dots or Boxes actually show the position in the frame where is your camera focusing.
The spot which blinks slightly generally shows which is the part in the frame where the camera is focusing.
You will not find many points in basic cameras like Nikon D3100 and D3200 and also in some basic cameras of Cannon.