Soccer has generally been the working class game, although recently it has also become increasingly a middle class pastime as well. Stadiums tend to be male dominated, with perhaps Spain the European exception, with more women and "family" attendance.
The two main cultures that developed in Europe from the 1970s onward came from England and Italy. The "hooligan" element certainly gained a strong foothold in the English game, and although much of the idiot aspect has been severely suppressed, the notoriety remains. (For example, most Latin Americans refer to all English soccer fans as "hooligans". A bit ironic, since the media is also full of stories of South Americans running around beating their referees to death.) Basically, roving gangs of violent thugs fought with other thugs inside and outside the stadium. English football literature is full of accounts of these morons running around beating each other up. The "hooligan" method of "fan" behaviour has spread throughout the world, and although in most cases it's a small minority of fans, unfortunately the sensationalist media has served to re-inforce the impression that soccer fans are violent lunatics that need to be met by a forceful police squad armed with truncheons.
The other major trend came from Italy, the so-called "Ultra" movement, which put more of an emphasis on massive choreographed theatrical displays within the stadium. Although violence did occur, it was not the main emphasis, and in most occasions, it was usually the overreaction of the authorities to "provocations" that caused the situations to escalate.
Germany took longer than it's rivals to develop the fan culture. Up until the early 1970s, the fans were largely well-behaved, and generally only cheered when there was something happening on the pitch. Occasionally you would see flags, and horns were not uncommon as a method of "firing up" your squad. On the other hand, obnoxious fan behaviour was rare. For example, I remember a crucial home match between rivals Wuppertaler SV and VfL Bochum, where some visiting Bochum fan took it upon himself to run in front of the WSV terraces waving his large Bochum flag. The WSV fans muttered about things like "if that idiot comes back, someone ought to punch him in the nose", but that was the extent. That type of "provocation" would hardly have been tolerated in many other parts of the soccer world, like the Kumbaya-ish Glasgow "Old Firm" or the Boca-River-River-Boca funfest, but for the time, in Germany, the fans had not yet taken matters into their own hands.
Things began to change somewhat by the 1980s, as fans became more "involved". Consider the following comments from Duisburg fan Tobias Wegner:
As you say there have been a lot of influences from the outside, but I think German hooliganism is just as old as the English hooliganism. In the old days most fans were "Kutten" or "Kuttenträger". A Kutte is a jeans-vest with thousands of patches sewed to it. Usually a huge club-Wappen was on the back. Security was not a big thing back then. So the different groups of fans usually got mixed after games and of course most of them were drunk. No wonder fights erupted more and more often. Soon most clubs had their own "security staff" (just regular fans who liked the idea i guess) who were basically trying to protect their people. So from now on (late 70s) the fights mostly took place between those guys. They were soon called Hooligans and it kind of became a sport.
Of course in the Ruhrgebiet it was a lot worse than everywhere else because of the density of clubs. Harsh rivalries were formed. The worst fights probably took place in the late 80s when Schalke played Duisburg. (Gelsenszene versus Forever Duisburg). Until then the Revierderby between Schalke and Dortmund was nothing. Dortmund mostly got their asses kicked until a strong group "Borussenfront" was formed to protect Dortmund Kutten. I recently saw a newspaper article about a game of Schalke here in Duisburg which claimed more than 700 injured and more than 100 arrested. And this is an example how alliances were formed: One day Duisburg played in Frankfurt against Eintracht and after the game the usual fights took place. Then cops came in and started to arrest people on both sides. In a matter of minutes both sides started a combined attack on the police and clearly won. They had a few beers after that and since then Eintracht and Duisburg helped each other out in Derbies (Duisburg against other Ruhrpott-Teams, or Frankfurt vs Offenbach or Mannheim).
Now Hooligans are not so important any more. Of course you can still find their banners in the stadiums each game and some groups are still very active (especially in the east) but most hooligans have Stadionverbot (stadium ban) in Germany and have to watch the game from the local Hool-Kneipe (a pub where regular fans just shouldnt go). Some say they keep a low profile too because they want to have a last big "party" in summer at the world cup. Many claim that it will be the last big "Auftritt" because most (ex)-Hooligans are well over 40, some even over 50. There are few young people joining because the press has made Hooligans very unpopular. Just in the past 2-3 years some Ultras seem to convert to Hooligans but that is a very few number. In general it can be said that in many cities, Hooligans are a myth, a feared group of middle-aged men who can be extremely violent and probably kick most peoples asses - but who are rarely noticed except by people who look for them. In the past years there have been very few incidents after games or even around stadiums. Most clubs still have one "Wald-und-Wiesen"-Gruppe. ("Forest and Meadow Group") They call each other up on mobile and then meet some place far away from the stadium and the police. It doesnt really have a lot to do with the game anymore."
The demise of the "Kuttenträger" and hooligan types has been replaced instead by the influence of the southland, and the "Ultra movement" has taken hold in many of Germany's largest stadiums. As German star players (think Brehme, Moller, Rummenigge, Hassler, Voller, Briegel etc.) continued to migrate to the wealthy Italian Serie A in it's hey day, German media began to pay more attention to leagues outside Germany. (Up until the mid 1970s, "kicker" might report the scores of foreign leagues, and if you wanted to watch something like Serie A highlights on TV, you'd have to watch one of the Gastarbeiter news program. I used to watch some of them (German subtitled) and then talk about them the next day at school with my friends, who could care less about the "Spaghettifresser". England was granted grudging respect, but nobody could name more than 2-3 teams.) The massive choreographed shows, fireworks and smoke certainly opened eyes among German fans.
The Italian Ultra culture started developing in the 1960s, and although it originally started as a movement among fans to drum up support for away games, it gradually morphed into an independent fan movement that not only staged massive choreography, but became a focal point against crass commercialization of the game by resisting overblown official club marketing and providing "political" protest. (Although some of the Ultra movements in Italy are known for political orientation: e.g. AS Roma largely left-wing, Lazio right-wing. Livorno are "reds", AC Milan's "Brigate Rossonere" a wordplay on the "Red Brigades" etc. In general the politics tend to be against club management and the corrupt federation rather than in favor of any ideology.)
With increased media coverage and the spread of the internet, German Ultra groups began to explode on the scene. Ironically, the first major efforts came from a club that traditionally has few fans: Bayer Leverkusen. The "Madboyz" stunned Germany with their pyrotechniques in the 1994 UEFA Cup match (ironically against Italy's Parma), transforming the tiny Ulrich-Haberland-Stadion into a madhouse. The impression across Germany was stunning, and soon groups popped up all over. With an intent to "boost stadium atmosphere and support for the club", the initial reaction from the clubs was certainly positive, as not only was it an attractive alternative to the hooligan element, but the great Stimmung (atmosphere) and choreography soon became an integral part of the fan stadium experience, and perhaps equally important, the TV experience as well. The gigantic banners being rolled down from the top rows and the non-stop chanting (increasingly internationalized, in many cases with "standards" such as "You'll never walk alone") serve as an electric impulse into the game experience. However positive this development seemed to be initially, soon clubs and other interests began to become less favorable in their outlook. First, the Ultras in Germany remain true to the spirit of the Italian movements: they strongly oppose the commercialization of the game, and obviously the clubs are more interested in merchandising, since the fans are basically only valued as cash dispensers. So many clubs have attempted to co-opt the Ultra movement and replace it with something sterile and "safe". Obviously most newspaper and other media reporters would rather report on "hooligan outrages" rather than well-behaved fans, so every firecracker or smoke bomb becomes hooligan warfare. And of course many regular fans complain that the Ultras are more interested in their choreography and half the time don't even know what's happening on the pitch. The leader with his bull-horn yelling out instructions certainly has his back to the field all 90 minutes. The Ultras respond that their emphasis is on the "unity of the club, of the traditional values such as club colors and badge". As such, the Ultra movements tend to be more suspicious of false demonstrations of player loyalty: the ubiquitous kissing of the club badge by the latest player mercenary after scoring a goal is viewed skeptically. To be sure, a player who has long served the club will be respected and cheered, but many of the trappings of "superstardom" that is promoted by club and media tends to be ignored. Also the fair-weather fans, the "ring tone generation", who complain when "their white adidas get stepped on" are vigorously opposed. These jokers are merely carpetbaggers who are only "interested" because soccer is currently "in", and they'll move on when something else becomes hot.
One outgrowth of the concern over violent fan behaviour has been the growth of the so-called Fan-Projekt, which can be found in every large and most medium sized clubs. In general, this is a club sponsored organization, but the level of independence varies from club to club. Some are merely repositories of club jersies and an attempt to co-opt non-official fan movements and separate fans from their cash, and others have more independence, and serve as a focal point for diverse fan-clubs with a quasi-official input into the club itself. These can be fairly large groupings: Schalke's "fan-union" encompasses some 1200 fan-clubs and over 25,000 members. The Ultras view themselves more as the vanguard of the fan-movement, and number around 800 hardcore at Schalke. For the most part, the official attempts to create a sterile fan support has been met by derision across Germany. The "members" of "Fan-Front Deutschland" or whatever the official DFB team supporters group are called are most likely to be 10 year olds who join so they can get a free World Cup sticker to put on their school books.
In general, most fan groups have no political orientation. To be sure, mostly in the east, the ex-GDR, various right-wing elements have established a foot-hold, most notoriously with the ex-Stasi club Dynamo Berlin. Wherever Dynamo plays in the east, there is almost guaranteed to be trouble. In the west, the most famous is political bent is the "anarchist" element associated with Hamburg's St.Pauli club. However, whether the majority of St.Pauli fans are really interested in what's going on the pitch is somewhat debatable, as many just seem there for the party atmosphere.
Certainly with the attendance boom in the Bundesliga, you can be sure that you'll never walk alone...