In keeping with that good advice, Mike, I'd like to take this chance to remind people that a post-flight inspection can be helpful too!
I have, on more than one occassion, forgotten my cell phone, or suction-cup pen holder that I had stuck to the pilot's side window before takeoff.
Fortunately, I fly out of a really great FBO, who has been wonderful about retrieving and holding such items for me post-flight. (Ok... I have to put in a shameless plug for them... it's Skyline Aeronautics out of KSUS, Chesterfield, Missouri. I gave out numerous copies of the first Chicken Wings books, and one CFII MEI there was a recipient.
http://www.skylineaero.com )