One of the most important skills in overhead lifting is the ability to create a secure, solid lockout position... part of this is being able to establish this position immediately. Often even lifters with great overhead positions are not adept at locking the bar in position quickly enough during a snatch or jerk to fully exploit that ability.
Conceptually this needs to be approached as aiming to secure the bar and prevent any additional movement (horizontal movement fore-aft, shoulder or elbow movement) as immediately as possible when reaching the receiving position. Additionally, lifters need to be attempting to lock the bar in as forcefully and aggressively as possible, and to maintain that force and aggression until choosing to drop the bar.
From a practical standpoint, there are a few ways to practice and improve this ability.
- Make the goal to lock the elbows and secure the bar overhead by the time the feet reconnect to the floor (note that in reality, the feet will reconnect before the overhead position is locked out in the snatch and jerk, but when a properly-timed lift is viewed in real time, they will appear to occur simultaneously).
- Keep the grip relatively loose - grip the bar only as tightly as needed to maintain control and the proper hand and wrist position overhead. Excessive grip tension slows the speed and limits the ultimate degree of elbow extension.
- Practice drills that allow focus and emphasis on this phase of the lift: for the snatch, tall snatch, dip snatch, snatch from power position, drop snatch, snatch balance; for the jerk, tall jerk, power jerk, jerk balance, push jerk behind the neck in split.
This issue is one of many related to the idea that lifters need to always remember the fundamentals of the lifts, and to practice every single lift with as much precision as possible. Every repetition performed contributes to the habits of the lifter in either a productive or counterproductive manner - which is up to the lifter.