[Burphel]

Get one that fits good. This is a safety issue as well as comfort. Go into a local shop, hell, go into all the local shops and try on as many as you can. Figure out what brands/models fit, and move on from there. Once you've found one that fits comfortably, try on the next size smaller. Most new motorcyclists buy their helmets too loose. Again, safety issue. A helmet that wobbles will not protect you as well. A tight fit will also make it a little quieter. If a full face doesn't hurt your ears putting it on and mush up your cheeks when it's new, it's probably too big. The comfort foam will pack down over the first month or so and loosen up. Helmets break in like old fashioned leather boots.

As for quiet, wear earplugs. Everybody claims their helmet is quieter. The only helmets I've owned that were noticeably quieter were Schuberths. And those start around $700 (mind you, they're great helmets).

Second thing, I would strongly advise getting one that's either ECE or Snell certified in addition to DOT. The DOT standard is actually pretty good, but our government doesn't require actual destructive testing. ECE and Snell do (this is why race orgs require them). For my brain, I don't want the first test to be when I crash. Fortunately, most reputable companies are building to ECE standard now and then just slapping the DOT next to it.

After that, it's all about features you like. I'm a heavy fogger and live in a wet climate, so I have to have pinlock-ready visors. This lets you add a sealed inner shield that makes it very hard to fog up. Inner sun visors are very handy for street riding. Venting schemes, lighter materials, fancy graphics, all that stuff...