Interesting comment from an official

[Adam]

Originally Posted by vbzebra

Officiating younger levels (middle school in this case), I found that quick "jump ball" calls are better for the safety for the kids. In every game, there were numerous alt possessions from the held balls. If player A has 2 hands on ball, and player B has 2 hands on ball. Obvious held ball. If A has 2 hands and B has 1 hand on ball, I think it would still be a held ball. But be watchful for B trying to get his 2nd hand on the ball and end up reaching in and commiting a foul. Had that alot too.

Here's how you can tell.

If, right as you're blowing the whistle, one of the players gains control of the ball, you've called it to quickly. This is a general "rule of thumb," not a hard-and-fast concept. However, it'll give you a guideline to judge your calls by, and will help you avoid calling this too quickly in the future.