I’ll speak as a patron of beer bars and beer halls, not as a DJ. I go to beer bars to relax, drink a bit, and hang out- not to dance. The places with the best vibes are the ones where the music is appropriate in energy and quiet enough to stay in the background.
BIG beer halls tend to be European (German, Polish, Czech), so the best music to play there would be traditional German music or the Polka, or anything else that sounds traditional and European. I’ve heard indie rock and Top 40 at big halls and they’re mood killers.
Small, intimate places vary more in their moods and atmospheres. If it’s a low-key place where people just relax and unwind, smooth, saxophone-y jazz works great. If it’s a sleek, sexy kind of bar, Deep House might be appropriate, but stay away from Nu Disco or anything too “feel-good.” I once went to a very dimly lit, swanky bar that had a great interior, and was about to sit down when loud Disco music started playing. My girlfriend and I walked out immediately. I LOVE disco music, but it was absolutely the wrong thing to hear in that environment.
So the important thing, like DJ Vintage said, is to know the environment you’ll be playing in. Visit the place and hang out for a while. Have a beer and get a feel for the place. There’s no magic formula that will work everywhere you go.