I always buy them online:
http://www.gerryweber-open.de/gwo_en, cost me £300 for tier 1 tickets for a week but last year I had tier 2 tickets for the final 4 days, which was £150. There are just two courts, the stadium and court 1 (and practice courts) and the court 1 is accessible with just a ground pass.
It can be hard to find somewhere to stay in Halle itself though there are local people who rent rooms during the tournament, it's easiest to stay in Bielefeld (there's an etap hotel in bielefeld too which is super cheap), 25 min train journey away, and local train fares in Germany are cheap.
The stadium is like a 5 minute walk away from halle centre, which consists of about 1 shop, 20 bakeries and a marketplace ...typical small German town. There are pubs, and a boring forest nearby.
The stadium is really nice and cosy, haha. And has a roof, which is always good! It's really easy to get close to the players as often they will come and sign around the side of the stadium after every match, and they also stay in the hotel which is attached to the tennis complex. It's really relaxed and awesome, I once saw Kohli just wandering around the site not being bothered haha. It has cheesy exhibitions and music and mascots which I find quite cute
You should deffo go! Lineup of players looks especially sweet this year. Aaaaaand if you want to see Fed, I'm pretty sure he'll be here in 2012.