You would use the knit or cable cast on, both of which make a better edge than the backward loop which is usually what's used at the end of the row. Turn your work as if ready to knit the next row, knit into the first st (or between the first 2 sts) and put the new st on the L needle. Repeat. Then you're ready to work the row with the new sts and old ones.
sue- knitting heretic