The ghost is "Stave I" is Marley, Scrooge's former business partner, and Marley performs many acts to get Scrooge's attention:
First, he manifests his face where the door knocker should be and gives Scrooge a slight scare; he scares him enough for Scrooge to check the back of the door when he enters the house to see if indeed the rest of his head is there.
Secondly, after Scrooges climbs the stairs to his chambers, he checks every room to see if Marley's ghost is anywhere to be seen. Obviously Marley has already gotten Scrooge's attention.
Once Scrooges sees that all is well, he changes into his night gown and sits before the fire to eat his gruel, and as he is sitting there, he notices that tiles that adorn the fireplace metaphorsis into a series of biblical images, and then they all change into Marley's face just long enough for Scrooge to notice them.
Scrooge, of course, brushes away this occurrence as a "humbug." But as he resumes eating his gruel, an old and unused servant bell begins to ring, and soon every bell in the house begins to ring in an attempt to get Scrooge's attention. And just as fast as they began, they stop to Scrooge's delight, but the delight is short lived, for deep in the bowels of the basement of the building, Scrooge hears a door slam shut, and then he hears the dragging of an enormous chain cross the stairs; at this moment Scrooge is paying close attention, and with in a matter of minutes Marley's ghost passes through door.
At this point Scrooge is paying close attention, and they have a conversation. It is in the conversation and the meeting that Marley really gets Scrooge's attention, for Marley relays his wretched tale to Scrooge explaining to him how the chain that is bound to his waist got there and the misery he has been experiencing for the last seven years, and warns Scrooge that if he doesn't heed his message that he too will suffer, but a far worse fate than Marley, Having gotten his attention, Marley can now set Scrooge up to meet the three ghosts.