See what your st to row gauge ratio is on the body - it's usually close to 2 sts per 3 rows or 3 sts per 4 rows. Once you determine that you pick up 2 sts every 3, or 3 every 4. The number of sts the pattern says to pick up might not be quite right if your row gauge was quite a lot different than called for. Look at the video for picking up on the Tips page (or it may be under Adv Techniques) for how; on an edge try to get your needle into 2 strands of yarn.
sue- knitting heretic