Begin by inserting your hook into the indicated stitch. Then slip stitch (Yarn over, and pull through the stitch and the loop on hook). Pull this new loop on hook up to desired length. (Tip: to ensure that your loops are the same height, remove hook and insert to previously created loops on row and pull all loops together, this will help you to maintain a constant height. This also helps to even the height of a row when working over uneven height stitches, just as shells or fans.)
Now comes a little trickier part, remove hook from loop and reinsert it into the same stitch the was just worked through, carefully yarn over and pull through a loop ensuring that the yarn is coming from the working end and not the loop just created.
Now chain to secure the long loop in place. Continue this process across row.
To begin the second row, you turn your work, and pull the working loop to the height of the long loops just created, insert hook in next Drop Stitch, and slip stitch, continue slip stitching each Drop Stitch across.
Also be aware that when using this stitch, it really improves the appearance after blocking. Blocking helps any twist that may be in the yarn to relax and give a more even overall look.
Check out a video tutorial here. Drop Stitch by Linda Dean