I can still remember getting my very first hit in a baseball game in grade school, beating out a little grounder to make it to first. The next two batters walked, and I was very excited over the chance to also score my first run.
The batter hit a hard shot, I ran as hard as I could...and I made it home! I ran back to the bench, expecting congratulations from the team, but received stern glares instead. And that's how I learned about the need to tag up on fly balls.