SEO for german keywords (google.de/at/ch)

Anyone here experienced with google.de / at / ch? (Germany, Austria, Switzerland)?

I've got a few questions:
- How do you determine correct keywords?
- Are there any relevant german directories, blogs, etc?
- Recommended hosting?

Basically you should speak German to be efficient in that; I think .de domains you must be resident to get them; use subdomain then.