There are a lot of choices around Berlin, most of them good. In any case you're looking at about an hour's drive outside of Berlin. There are a couple that are closer, but they have the disadvantage of being under low airspace shelves, so it is more difficult to go x/c from them.

The culture of German clubs is very different from American clubs. Generally, compared to American clubs, there can be more focus on the club itself than on the flying. Because of this, private ships are not looked upon favorably in some cases. If you are flying a club ship, you're generally expected to be at the morning briefing at 9am, and stay until the debrief when the sun goes down. When you're waiting your turn for a club ship, you'll be helping at the flight line. Most people with their own ships spend their time in the air instead of on the flight line, and so to some degree the private owners are seen as not pitching into the club.

Two clubs I can comment on a

FCC Berlin (Lüsse): Extremely high standard of facilities and club equipment. Somewhat bureaucratic. They require a large deposit and rental fee to base a ship there. No real old-timer presence.

FK Brandenburg: Very friendly, slightly shabby facilities, some old-timer presence (the club has an SG 38 that they pull out periodically), officially not currently accepting new private ships, but you may be able to convince them.

It's also worth making a trip to Reinsdorf as there are three different clubs at that field. I don't have any personal knowledge of them though.

-Dave