This is for a crochet cast on using a crochet chain.
(crochet chain) With crochet hook, make a chain with project yarn that is the number of stitches to be cast on. Put the last loop on needle. You are going to pick up the garment yarn through the loop on the BACK of the chain stitches. With the chain RS down, the loop looks like it is holding two chains together. Begin in the next loop, *Insert the tip of your needle into a loop, wrap the yarn around needle to create stitch and pull through loop. Rep from * for the correct number of stitches.
See also: sc, dc, tc, hdc, YOH, chain, join (crochet), join chain (crochet), crochet CO