As it says you need to play 100 ranked matches, obviously as "OlsAbsss x" says if they quit then the game won't count. They can quit even after the whistle blows as long as they don't see the menus, so don't expect that you'll get the game to count even if you make it to full time.
The easiest way to avoid people quitting is to select custom ranked match, and choose less than 10% DNF. I have only had 2 quits in 62 games since I did this.
Please note that matches played before the EA reset due to the flag glitch WILL still count, as the 62 games I mentioned were after the reset and I received the achievement on the 61st of these games.
As the results don't really matter make sure you go teams that are at least half a star lower than your opponent to allow you to get the following achievements.
The In for the Win achievement in FIFA 11 worth 20 pointsTake a Head to Head Ranked Match to extra time with a weaker team
And also go a different team each time to get this one...
The Experimental achievement in FIFA 11 worth 31 pointsPlay 5 consecutive Head to Head Ranked Matches with different teams
According to "another benco" and "ziplobthud" games played here will count towards the Around the World achievement.