When David and Liz have a trouble with a flat tire on their car, the hub cap on the wheel with the flat tire goes from being fitted to being removed several times.
In the kitchen scene where David is preparing turkey, the length of Ned's pizza slice varies greatly between shots.
When Ned wakes his friend to vouch for David's credibility, according to the alarm clock it's 12:46am. However, when the conversation is over it's 12:43am.
Liz would have had her own bedroom in that huge two story house so there was no need for her dad to put her in a guest room.