Double Knitting Question

[stefcap]

I am going to start a double knit afghan shortly, using two colors. I am not quite sure how to cast on, though. The pattern calls for 100 sts, and I am wondering just how to go about doing it. Do i alternate between the two colors while casting on (i.e., cast on 1 st with A, then 1 st with B, and continue like that for the 100 sts with 50 of A and 50 of B), or do I cast on 100 with A then 100 with B, or 50 with A then 50 with B? I am so confused

[SabrinaJL]

I'm working on a double-knit scarf right now and I just held both colors together to cast on. The instructions I got said "Cast on 17 stitches with both strands held together. The MC should be on the right side of every cast on stitch while the CC should be on the left." It