Heh, I was actually sitting in the parking lot at the drugstore the other day with a NFPA biner clipped to my steering wheel and doing some knots...
For your harness tie in I'd recommend a "figure 8 follow through" with a stopper knot, or a double-loop figure 8 like Quercus mentioned. We used the figure 8 follow through to tie in thousands of people over a decade where I worked and never had any problem; just leave plenty of tail, don't tie them short.