When Danny tells Steve how they first met he says "Four years ago you came knocking on my door" They actually met when Danny was investigating John McGarrett's [Steve's dad]house found Steve there and they drew their guns on each other.
When Kono flips the image from the table computer to the screen McGarrett's right hand is resting on his badge but when the shot changes to the reverse angle his hand moves from his stomach to his badge.
When Mcgarrett (O'Loughlin) was interrogating Dawn Hatfield (Sasha Pieterse) in the house he called her Amber instead of Dawn.