One of the numerous steps in learning the violin is the mastery of shifting. Technically complex but essential, it involves a combination of muscle, tactile, auditory, and even visual memories.
Here is a list of 10 tips that can help you improve your technique:
1 – Move the whole arm as a single piece: fingers, hand, wrist, forearm and elbow.
2 – Consider the elbow as the initiator of the shift. Indeed, the distance traveled by the fingers on the fingerboard is greater than the one traveled by the elbow. It is therefore easier for the brain to memorize the movement of your arm than your fingers’.
3 – Relax your fingers. The movement of your elbow should naturally lead the movement of your left hand, which is to say of your fingers. But if your fingers are clutched to the fingerboard, they will remain anchored to their initial positions or randomly move with difficulty.
4 - Relax all your fingers. Do not forget your thumb! Avoid as much friction as possible between your thumb and the neck. Some even recommend no contact at all.
5 – Loosen the pressure in the moving finger while shifting. The finger should touch the string without being in contact with the fingerboard. The three steps are: (a) lift, (b) shift to change position, (c) drop to play the note.
6 – Make sure the violin is not supported by your left hand. It should stay in place without using it, allowing the latter to move freely along the neck.
7 – Maintain a fluid motion. Do not go too fast at first. The first step is to reach the desired notes. Speed will then gradually come, along with confidence.
8 – Decrease bow pressure and speed when shifting.
9 – Use your ear. As finger pressure is applied on the string while shifting, it still emits sound. So use your ear to guide your decision and improve your accuracy.
10 – Persevere! Learning shifting is a long, repetitive, frustrating and sometimes painful (my poor fingers…) process. But it is important not to skip steps to acquire a serious and precise technique.
Good luck! 
…, my apologies.