You had to try many times before you were able to whistle. You know that if you don't whistle once in a while you will have to learn to do it again. Marble shooting is the same as these things. If you want to be a marble shooting champion, you will have to work at it. You will have to make it a habit of practicing your shooting as often as possible.
Some champions say that they had to practice daily.
The easiest way to practice shooting marbles is to make a line of target marbles. Then go down the line and shoot each target marble. Your first shot should be about two inches. There are many ways to decide which marble is the best shooter for you. Size and roundness are more important than color.