Hello there Angus. If you don't already have a .22 rimfire bolt action, get one.
If or when you have one, then buy a couple or twenty blocks of cci standard and start using it. Join a local club that is set-up for rimfire if you don't have somewhere safe to practice. Work on shooting standing, sitting and prone. Concentrate on perfect trigger release and follow through. Watch your shot go through the target and call your shot through observing the recoil pattern.
The only way to become proficient is practicing good habits, and thousands of rounds downrange. There are no shortcuts, but a competent coach can help you from acquiring bad habits that may take you a lifetime to unlearn. Ego is your enemy, focus on small improvements every time you shoot. Have a plan on what you wish to do each time you shoot, but the goal must be realist and achievable to where you are at.
Avoid bullshit and evaluate your performance each time Write it up to cement lessons learned and achievement attained.
Rimfire is cheap practice and shows up faults in technique that are hidden in the recoil of a centrefire, and all skills learned are common.
Good luck.
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