I noticed while clipping a runner that I had only tied in through the lower (leg loop) attachment point of my harness on one of the half ropes that I was leading on. Easily corrected by clipping the other rope and retying correctly. This was while leading through, having seconded the first pitch.
1. As the belayer for the first pitch I had not tied in until my leader was at the stance. This prevented my having tied in incorrectly being spotted by a 'buddy check' Always tie in before the leader starts climbing and check each other.
2. I habitually pass the ropes up from bottom to top when tying in using a figure of 8. Unless there is a good reason not to, then passing the ropes top to bottom would ensure that even if the rope is not threaded through both parts of the harness it will be threaded through the waist belt attachment point.
Trad rock climbing
Rescue Services Involved?