For La Liga, tickets generally go on sale to the general public about 4 weeks before the start of the competition once the fixture list is announced.
Are tickets on sale for FCB v R. Madrid via the same procedure?
Regarding FCB v R. Madrid, there are usually two sales procedures: the first on the same day that other matches go on sale (intended only for members without season tickets), and the second, a few days before the match, as long as there are seats available from the Seient Lliure system.
For the Champions League, tickets go on sale once the group draw has been made in early September. If and when the team qualifies for later stages, tickets are put on sale as quickly as possible.
For knockout matches there are usually two sales procedures, the first (for non-season ticket holding members) with a finite number of tickets, and the second, a few days before the match is played and as long as there are seats available from the Seient Lliure system, which initially go on sale only to members and only in cases of high availability go on sale to the general public.
COPA DEL REY
For the Copa Rey, sales open the day after the draw or very shortly after.
In the event that FCB are to play R. Madrid, the sales procedure is the same as for a league match.
OTHER COMPETITIONS OR GAMES
For the Joan Gamper Trophy, or in a possible Spanish Super Cup, tickets usually go on sale about 3 to 4 weeks before the match is played.