• Basically you want to clean the pads and rotor. Some like the remarks below use a different pad. Change the stock pads to semi-metallic ones from Disco Brakes. That solved the squealing for them.
• I would center and adjust each brake. Oiling is not recommended, lubricants on the pad are very hard to clean off.
  
• To center the caliper:
  
1. raise the wheel, loosen the adjuster bolts so the caliper is floating and flopping.
   
2. Then tighten the torx hex nut, evenly inside and out, to bring the pads in to the disc at the same amount.One click inside, one click out side, until it is pinching hard on the disc and won't turn anymore.
   
3. Next tighten the adjuster mount bolts on the caliper.
   
4. Now back out the torx bolts on the pads evenly about 3 or 4 clicks on both sides. Flex the brake lever several times. spin the wheel. if still rubbing, loosen one more click.
   
5. You may have to repeat, a little bit of practice helps.

• If your brake pads are brand new then they need to be bedded in. Either buy new organic pads or sand down the ones you have, then follow these instructions to bed the pads.
• The brake pads are NOT ideal when they are evenly spaced form the disk (rotor). The Avid brakes have one fixed and one moving caliper. The "inner" caliper is fixed, and the gap from pad to rotor should be TWICE AS LARGE as the "outer" ["outer" is identified as the one that moves - may not be same as orientation on ELF]. When you pull the brakes, the "outer" pad moves toward the rotor, makes contact first, and actually bends the rotor toward the inner pad (when I first saw my rotors bending, I tried to adjust the pads for even spacing -- apparently this is the OPPOSITE of what you should do -- they got worse). See this article for the full step-by-step of proper adjustment: Avid® Mechanical Disc Adjustment
• Tom of OT suggested that I clean the brake caliper and the area around it with soapy water scrubbing with a toothbrush, which I will, but just pouring soapy water over it from the outside and from the inside helped considerably.
• Grit on the disc can make some pretty heinous noises. I spray the brakes down with any leftover water in my drink bottle occasionally.
• YouTube video showing How to Adjust Avid Disc Brakes

Helpful Links

• Squeaky Brakes (from Organic Transit)