How to handle the exception while calling the WCF web service?

How to handle the exception while calling the WCF web service?

We have developed the web application, here we are calling third party web
service to fetch the data, In this case we are getting some exception
while calling the WCF web service, some times we have to fix the issue in
our web application, some times they are fixing the issue in WCF Web
service code side.
How to identify the exception is in our code or WCF web service exception.
if we found this then we can easily tell to user please contact webservice
persons or us.
How do we identify this, What are all the exception handling that we need
to add in our web application code. Please advise.
Thanks
Mayil.M