That's a little vague, can you provide some more detail?
What have you done to trouble shoot so far?
What application are you printing from?
Local or network printer? What kind/model? What OS?
Did it ever print correctly? Did the error just start? What was the last thing that changed when it quit working?
Post whatever detail you can and we'll be glad to help.
If it is local and parallel then the most common problem is not having you parallel port set to normal and not epp or ecp. Normal is basically one way communication and the device driver is waiting for a response from the printer that will never come.