Accommodation in Germany: scams you should look out for

Scams in the German rental and property market are very rare, because everything is well (some say overly) regulated.
Of course the common caveats apply: Never send money before you have seen the property, landlord and signed a written contract. And keep in mind: If something seems too good to be true, it probably is.
Once you follow that, the only pitfalls are being overcharged (here it helps to know the market and stick to your budget) or being rejected (incl. for being a foreigner, which is illegal but difficult to prove ...).
Many of the popular cities in Germany face a shortage of rental (or even for sale) properties, so be prepared for a long and sometimes frustrating search!

^^^
Yep, scams are generally pretty rare. That being said, I've seen -quite- a few listed on websites like Craigslist that were/are popular with internationals but not so popular with Germans. Generally, it's better to look through a German listing site for real estate, roommates, or things like that (think ImmobilienScout24 or WG Gesucht, which also has listings for small apartments). Scams on those are incredibly rare.

As beppi said, be very wary if you're asked to send money upfront sight unseen, unless you're dealing with a vetted estate agent/realtor, in which case you're hiring them to find the apartment or house for you. And be immediately skeptical if you can't see the apartment at all. You (or someone representing you) should always be able to make an appointment for a viewing. If that can't happen, it's not legit.