Find a flat area on a practice green and put tees 5,10,15,20… feet away and hit a bunch of putts until you get a feel for each distance

When it comes to making putts it’s all mental assuming your stroke is not horrible.

Read Bob Rotella’s The Golfer’s Mind. My golf improved so much after I read it. It’s probably most helpful for people that have been playing for a while and compete since that’s when the mind starts to betray you, but great read otherwise too