I would like to see the changes that my co-workers have made before I accept the incoming changes.

So I start by getting the status

svn st -u

...which tells me that I've got an incoming change

    *     9803   incomingChanges.html
M         9803   localChanges.html
M   *     9803   localAndIncoming.html

I can see what I've changed

svn diff localChanges.html

...but how can I diff incomingChanges.html and/orlocalAndIncoming.html to show what has been changed, and how it's different than my working copy?