Look down at the top edge of the work. It should look like a braid, with a front row of loops and a back row of loops. The front loops and back loops line up with each other in pairs, and each set of loops counts as one stitch.
When working stitches on a beginning chain, the hook is traditionally inserted in the back loop of the braid to begin each stitch (although there are other ways of working the beginning chain, as described in this post). When working stitches on any other row in the project, the hook is inserted in both loops of the braid unless otherwise indicated in the pattern.
Sometimes when using very textured yarn or eyelash yarn, it becomes difficult to see the stitches you have worked. In this case, it may be helpful to hold the work up to the light to make the stitches and rows more apparent.