What is the seeding process?

I'm playing in my first tournament and I'm curious as to the process for seeding players into the second round. First, is the seeding done by rating just before the second round starts, or by standing after the first round (or conceivably by the rating at the start of the tournament)?

Second, what is the algorithm? I'm guessing that player #1 will go into one group then #2 into a different group until the top 25 players are each in a different group. Then what? Does player #26 go into the group with #1, #27 with #2, etc.?

Please see http://www.chess.com/tournaments/help.html#groupings for more information on how seedings are done in tournaments.

@Patzer24: There is no information about the second round seedings.

The advancing players are seeded according to rating just before the second round starts.

The groups are not formed as described in the help entry.

"For example, in a 25-player tournament with 5 groups and 5 players in each group, the top rated player goes into Group #1, 2nd highest rated player into Group #2, 3rd highest rated player into Group #3, and so on. After all groups have one player, it starts all over again at Group #1."

The groups are formed opposite to this. The lowest rated players goes into the last group, the second lowest in the next group up and so on. The difference is seen where at least one group is short a player. The highest rated will not be in Group#1.

See here the first four groups are short a player and the highest rated at 2134 is in Group #5.

I also wonder about that.

When round two starts, how are the seeding than?
The same ratings as they had before round 1?
the ratings they have now before round two?
or the standings after round 1?

And what happens if in a 1800-2000 tournament, one or several players exceeds or drops rating to f.ex 1700 and 2100 before round 2 starts?
Do they still qualify for next round?