fish in a barrel, denial ain't just a river in Egypt

like shooting fish in a barrel : ridiculously easy

Making mockery of George W. is like shooting fish in  a barrel.

Denial is not just a river in Egypt.

This expression(?) uses the similarity between the way the name of the rive "The Nile" and the theraputic term "denial" sound when spoken. It's a humorous way of saying that someone refuses to see what's obvious to everyone else.

Tipping is not just a city in China.

A not too subtle suggestion to leave some cash to the provider of a service in the form of a tip. It is paying off many of "-ing" cities in China - Peking, Beijing, etc.

behind (ahead of) the curve

at the forefront of (or lagging behind) recent developments, trends, etc.

ex) The Fed may be a little behind the curve.