the mold will grow between the buds and the stems, usually starting at the main stalk. It then consumes outward, and the first easily visible signs are white fuzz in the buds, then turning brown to black when the mold spores are mature. They are teensy littl microscopic Zero gravity buggers that will infest more than just your tent. It requires all pots, equipment, walls, tents, and lights... everything!!! must be sterilized before you use the grow area again.
You can try to save some bud by clipping out each section of mold, but be careful to use alcohol on your sheers/scissors for every single cut. Or you are just spreading it.
Once you have all visible mold gone, you can dunk the buds in a water bucket with a bit of baking soda and a lemon juice, then a clean water dunk, and speed dry them.
But like Renaissance Redneck said, you CANNOT smoke it if it has any mold. You have to be real careful about that.