Requirements:
None.

Method:
The achievement-description is self-explanatory.
Usually this would mean I would not be writing a guide.

However I think it is important to point out that Single Player Tournaments (Pro-Takedown Tournament) count towards this achievement even after the player has reached level 25.

Important Notes:
If you find yourself struggling to win tournaments then have a look at the forum for this game and look at the thread "I like this game".

Recommendations:
I would suggest to get this achievement in single player games. That way you do not lose any credits from your bankroll. As a minor disadvantage there will be no XP after the player has reached level 25.