Watch as much baseball as possible.
Even if you don’t have a scorecard in front of you, think through how you would score each play. Think about different variations on plays that happen. What if the runner would’ve beat out the throw? Would that have still been an error? Keep pushing the hypotheticals, what if the right fielder hadn’t hesitated and threw him out at second base? It’s great if you have somebody else to bounce new trivia off. Then the next time you have a chance, look it up in the rulebook.
The more possibilities and situations that you can think through, the more you will be prepared for next time. I generally find that there are one or two plays in each game that you’ll see once or twice each summer, the other 95% of the plays (groundouts, flyouts) happen every game. The problem is that when you encounter a rare play, you can’t ask the players to give you an extra minute to think about it and record the play. It’s about preparation for those select few plays that separates somebody who really knows what they’re doing and 98% of the fans out there.
If you’re watching an MLB game and a wacky play comes up, take advantage of the GameDay feature on mlb.com. Every play of every game is recorded, with every call being made by a major league official scorer. If they don’t give scoring info on the telecast, just remember that the play occurred in the bottom of the second and check it out the next time you get a chance.