Actually, I don't. I have an LHT, and thus cantilever style brakes. Only the front brake was squealing. I took my bike to a bicycle shop. He pointed out my brake pads were low. I have since:
1) Changed both front and rear brake pads
2) Lightly sanded down both my front and rear rims. (120 grit)
3) Toed-in the pads.
Now, I still have the same situation, i.e., ONLY the front brake squeals. I now have much better stopping power, but now my front brake squeals in all weather conditions, whereas before the front brake only squealed when it was raining, or when my bike was left out in the cold (cold rims and such).
I toed in the front brake pads. It squealed. I re-adjusted so the pads were NOT toed-in. It squealed. My tire is true. Before installing the new pads, and before lightly sanding the rim I made sure to wash the crud off my rim as best I could.