Please excuse the filth.
See the above pic. In the center is the throtle body. Simply disconnect the hoses at either end and remove the bolts which mount the throttle body to the intake manifold. Unplug the electrical connector and the throttle body should be free.
Use a commercially-available carburetor cleaner to remove all the gunk buildup inside the throttle body, being very careful to not get any inside the stepper motor attached to the side. The easiest way I know of to prevent stepper motor contamination is to hold the throttle body with the stepper motor at the top so no carb cleaner runs down through the small hole for the connecting shaft.
You should also be able to push the plate open a little by hand to clean the edge and where the plate makes contact with the throttle housing. Reinstallation is the reverse of removal.