Before I get into pattern instructions, I thought it would be best review what we've learned so far. When I first learned crochet, one of the things that always confused me was where I was supposed to be inserting my hook.
Actually, there is really no *one* right or wrong way, and it actually depends on a couple of things. First of all, often the pattern instructions will dictate where the hook is to be inserted, and if you are crocheting without a pattern, you are completely free to choose whatever you wish to achieve the final look of your project.
Generally, inserting the hook in only one loop of the previous row, will result in a horizontal "bar" across the work in that row, and on one side of the finished work. Inserting the hook in both stitches will usually eliminate that bar.
Experiment with different techniques, and see which you like best. Again,the appearance of the finished effect will determine your hook placement.
Crochet 101 - STITCH & HOOK PLACEMENT CLOSE UP DETAILS
Used with permission and with appreciation to Teresa.