Just got this achievement, so I figured out the most effective way to do this.
If you're playing "legit" or boosting, either way there are certain criteria to get a win.
Firstly, it has to be a ranked exhibition xbox live match, that means that you can not change any of the rules in the custom match settings. It only seemed to work for me when searching using quick play.
Once you select quick play, and if there are no games available, you will get a prompt, suggesting that you either search again or create a game.
If you're looking to boost this achievement with someone else, you can do one of two things.
1) Play through the whole game after finding each other.
2) Have the person that isn't winning quit. HOWEVER, the person that is supposed to get the win HAS to be the Host (The person that created the match) or else you do not get the win, and at least one pitch should be thrown.
I just tried both methods earlier today, so I promise both work.
You can check your wins at any point by checking the leaderboards in the xbox live menu of the game.
Win 10 times and you'll get this achievement.
Remember as well, that if you're looking to get this without a boosting partner, that baseball is a primarily American sport. That means that the prime times to find people are during the day, somewhere around 5 pm Central Time or so.