If your shots group low and to the left most likely you are jerking the trigger instead of squeezing it.
If your shots group high to the left - say in the 9 o'clock to 12 o'clock position - you are probably anticipating the recoil and pushing the firearm up. This is called "riding the recoil". Groups in this area are also caused by lack of follow-through.
If your group is consistent at about 9 o'clock you most likely do not have your finger on the trigger properly. You are probably squeezing at an angle instead of straight back.
If you group is high to the right you may be "heeling" the firearm - anticipating the recoil and pushing with the heel of your hand.
If your shots group fairly consistently to the right in the 3 o'clock area you are probably "thumbing" the gun. That is, as the gun goes off you are pushing on the side of the frame with your thumb.
If your group is consistently low, say in the 6 o'clock area, you may be "breaking" your wrist, that is, anticipating the recoil and cocking the wrist down. Low shots also come from improper follow-through when the shooter relaxes too quickly.
If all the shots are hitting right, low, say in the 4 to 5 o'clock area, you may be tightening your grip just as the gun fires. This is another form of anticipating recoil.
Above assumes right handed shooter.