If you are picking up sts all the way around the runner, you will have to accomodate for guage differences. Picking up along the CO/BO edges, will be different than picking up along the sides.
Work a swatch in whatever pattern it is you want to make the border in. Determine your guage. Then measure the lengths of each of the four edges (or just two as the two sides and two ends will be the same) and figure out how many sts you need to pick up to cover that distance in your desired stitch. Then pick up the sts and knit on!