I'm asking how the system works where the teams at the ESL touraments (Katowice, Cologne, etc.) choose the maps at the group. Please tell me a lot of details because I'm developing this system for amateur clans which doesn't have the oppurnity to use the official system.
It's a bit late, but the ESL uses these rules for their championships:
(The accepted answer is a bit inaccurate.)
Best of One:
Ban A - Ban B - Ban A - Ban B - Randomized map out of the three remaining
(Teams select 4 maps not to be played and the map to be played will be a random map from the remaining ones.)
Best of Three:
Ban A - Ban B - Pick A - Pick B - Randomized 3rd map out of the three remaining
(Teams select one map each not to be played, then pick a map to be played. If a decider is needed it will be randomly selected from the remaining maps in the pool.)
For the most recent competition, ESL One Cologne, Maps were chosen as so:
In this example, we will use two teams, team A and team B, and all the maps in this pot will be in active duty.
Team A will ban a map from the raffle, in this case, let's say they ban Cobblestone.
Team B does the same thing. let's say they ban off Dust 2.
Team A repeats, banning cache. Team B follows, banning Inferno.
Team A bans Mirage. Team B bans Train.
There should only be one map remaining, and this map would be Overpass.
Therefore, Overpass is the selected map.
In a nutshell, you ban off maps until one remains, and that will be the map you play on. The maps that you ban should be maps which you think the opposing team is good at.
If I'm not wrong, another way of doing this is to ban off maps until 3 are left, and picking one randomly from the three.
There are many ways to go about doing this, and there are no real limits to do it, but the two methods stated above are the most common (mostly the first one)