At the campfire scene, whenever the camera shows Scott, Mike's hands are hanged to each other, but whenever the camera shows Mike, he is playing with piece of wood.
When Mike and Scott are biking it to Idaho, and Scott is having trouble starting the bike, the bike is steady on its stand in the front shot, when Scott is still astride it. When Scott hands the bike over to Mike, and the shot is from behind, Scott's hands are back on the handlebars, they were on the tank, and the bike is not on the stand.
When Bob approaches Scott in the bar near the end of the film, two marks of black gaffer tape can be seen on the floor.
When Mike is in Idaho he has a clear view of Mt. Hood. Not only is the mountain too far away to see (over 200 miles), there is another mountain range lying between Idaho and Mt. Hood, blocking the view.
(At 12.45) As Mike goes to look out the window at the back garden in the old ladies house the boom mic is visible reflected in the window.
Mike's brother Richard speaks with a New York accent even though he's from Idaho.
In Scott and Bob's final scene together, Bob says Scottie's wearing a three-piece suit, but we see him wearing a two-piece suit.