How to do ExceptionHandling

can any one explain, how to do ExceptionHandling?. when i get an Error in FileReading or Writing File to Somewhere(Publish/Subscribe).
i written try and catch for a Service. but system has to throw a perticular error message to the client and process has to be stop.
and one more Query is: how to set acknowledgement. i would like to know wheather the Target application is received the file ot not.?

Check in the WmSamples package errorHandling scenarios(sample.errorHandling:approach1,approach2)for better understanding.