If by when you say it doesn't work, it might be that when you locked the object it's position is somewhere else, or at 0,0,0 in coorilation with the camera. Instead, either lock the object before positioning the camera, then position the object at 0,0,10(just to see where it is, remember, when you lock an object, its coordinate system is changed to be based around the cameras postion, so 1,1,1 wouldn't necessarily mean 1,1,1)
The problem with locking a main character object is that you would have to change the angle of the camera, and not the object, if you want to turn, say, right. The reason for this is that the object is locked to the camera, so 0,0,0 is the cameras position and angle, NOT the worlds postion.
Check the box to see a sample code, this will cause the camera to chase the object, just place CHASE_CAM(ID) in the main loop, oh and ID is the object number, so just make ID = 1. Hope that helps