@Ami: Re setting up your own WG. I can only tell you how it works in Vienna, but here a lot of larger flats are advertised as "WG geeignet". In such a case the landlord actually wants to rent the place out to students etc. - probably because the place needs doing up and he doesn't want to make that investment at the moment. Still, a flat like this must be up to some kind of minimum standard, at least, and it is assumed that students etc. won't be too fussy about how nice it looks.
Even renovated flats can be rented as "WGs". One of the flats we looked at in this building has since been let to three young professional people - presumably they could afford it, the rent being 1100 euros per month. But that is more affordable divided by three than for a couple, for example.
So here the method simply involves finding a flat advertised in the newspaper (or Internet) and asking the landlord if it is suitable for use as a WG.
As for the responsibility issue, you could try to find at least one potential flatmate first (preferably a German local - that will be helpful when talking to landlords) and look for flats together, then share the costs for the deposit etc. (you can always charge part of this to the other tenants later). Then there is also the cost of getting the power and telephone etc. connected.
But you mightn't have time to do this at the moment, anyway, though you could keep it in mind for next time.
Mausling's suggestions are good and realistic. Think about what kind of person you are and what kind of people you would like to live with. Will you feel comfortable if you come into the kitchen in the morning and someone casually offers you a joint while blowing his nose on your favourite teatowel, lovingly embroidered by your dear departed Great-Grandma?
Will you be happy if the flatmates are constantly inviting friends over who stay the night/play loud music/raid the fridge and pantry..? Or will you be wanting to invite people over? In that case you will want to avoid boarding with elderly people, for example, who often stipulate that no visitors are allowed.
As for cleaning - in some WGs this is unheard of, though they won't mind if one person does all the cleaning, as long as they are not asked to help. In other WGs you may find cleaning fanatics who insist on a weekly cleaning roster.
My favourite quote from the unhousetrained pot-smoker: "Warum sollte ich was für Putzmittel zahlen, wenn ich eh nicht putze?"
In Austrian (I presume also German) WGs people tend to buy most of their food separately, and communally only for certain items, e.g. flour, milk, coffee, dishwashing liquid, toilet paper (but it has to be agreed upon - you can never assume.)
Some WGs have odd bathroom 'solutions', too - to come back to Mausling's point about supposed "prudishness". Often the shower is directly in the kitchen, without a door, resulting in unavoidable nakedness, or the toilet is separated from the kitchen only by one door (in other words, the toilet is in the kitchen!), resulting in other unavoidably awkward situations. This is a result of the aformentioned habit of landlords to rent out unrenovated flats as WGs. In one flat I was in I had to go through the bathroom to get to my room!
Ja, ich bin WG-erfahren - und WG-geschädigt! :-}