There have been six draws in the first 16 games of the World Cup, and only three teams (Germany, South Korea and the Netherlands) have won by two goals or more. At the moment, Groups A and F are a four-way tie, and in Group C the two favorites to progress, the U.S. and England, are tied for second with one point apiece, and the remaining games may not divide them.
No surprise, then, that plenty of readers have asked for clarification on how FIFA goes about ranking the groups.
In the group stage, the tables will be set according to number of points, and teams that have won the same number of points will be ranked by goal difference (which is why Netherlands leads Japan in Group E). If two teams have the same number of points and the same goal difference, the one with more goals will be on top. In Group H, Chile and Switzerland can't be separated at all because of identical 1-0 victories, so they're ranked alphabetically for now.
The top two teams, of course, go through to the knockout stages after playing all three group matches. According to FIFA regulations, if two or more teams remain equal at that point, three further criteria come into play.
First, the side with the most points in the encounter(s) between the tied teams takes precedence. But, for instance, if there's still a tie between England and the U.S. once the group action is finished (i.e. if each team matches the other's result and score line against Slovenia and Algeria), this won't help, because both earned a point in their meeting on Saturday.
The next criterion is goal difference in the group matches between the tied teams. This is likely to be able to separate three tied teams if points don't, but won't always help -- in the hypothetical two-way tie between the U.S. and England, goal difference still won't do it.
Teams that cannot be separated by goal difference are then ranked according to the number of goals scored in the games between the teams concerned. Again, if three teams are level in a group, number of goals is likely to put daylight between them.
In our hypothetical two-way tie between England and the U.S., of course, it still doesn't make a difference. At which point, the FIFA organizing committee gives up and draws lots. That's happened only once in World Cup history, between Netherlands and the Republic of Ireland in 1990. England escaped trouble by beating Egypt, which left the Dutch and the Irish level for second and third and they'd drawn 1-1 when they met. In those days, the top three teams all went through, so when the Netherlands got the bum draw, it only decided its next opponent (it got West Germany, Ireland got Romania). In South Africa, a similar situation would send the loser home.