Originally Posted by Myosmith

Full strength Simple Green with a bit of Dawn dish soap will easily remove WD40 with no danger to lables, plastic, rubber, etc. Soft tooth brush works good for cleaning brake components. Once the oil is removed, rinse with hot water until no more suds, then dry by hand and/or with a compressor nozzel. If you don't have a compressor, a few blasts from canned air will get the water out of any hidden spots. A couple drops of appropriate lubricant on pivots and cable end should be all that is needed.

Once the brake pads are clean, lightly roughen the braking surface with 400 grit sandpaper. New brake pads may have a mold release on the surface, similar to that on some new tires, and a bit of wear removes it and makes them work better and more quietly. Proper alignment of the brake pad to the rim, as mentioned above, will also quiet brake howl and keep the brakes from feeling "grabby".

New parts like rims and brake pads need a break-in period, so give it some time and a couple hundred miles. They will wear to fit each other and usually all will be well. If braking performance is poor or the excessive howl persists, talk to your LBS about different pads. Everyone has their opinions on which pads are the best but unless you are doing a lot of long steep downhills at break-neck speeds, the mid-range pads from your LBS will perform just fine. Just avoid the super cheap pads and stick with respected brand names.

BTW,

Brake = device designed to impede motion
Break = a structural failure or time to get coffee