Continuity mistake: When Pinkman and White are having breakfast in the diner, the items on the table keep changing in each shot. Specifically, the jelly, the milk, the cup with the cream and, most noticeably, the rolled napkin with the cutlery inside: Sometimes folded, others opened.
Other mistake: When Walt is ringing Jesse to find out where he is, the call goes straight to voicemail. However, when he rings Jesse from inside Jesse's bedroom, the phone rings before going to voicemail. The mistake being that the call should have gone straight to voicemail.
Continuity mistake: In episode 2-10, Walt installed a new gas water heater. The gas lines run from the left wall to heater mounted on the back wall of the utility room. In episode 4-11, Walt is in the crawl space under the utility room. The gas lines are no longer visible.