A dropped stitch can seem like the end of the world but with some practice and patience you can pick them up like a pro and not bat an eyelash. Dropped stitches used to be a heart attack for me. But once day I decided I had had enough. Too much stress for such a small thing. I knit up a stockinette swatch (4 in. by 4 in) square and set to work practicing. The Stockingette provided me with practice for both knit and purl stitches. Since all knitting is made up of these 2 stitches practicing them will be your bread and butter. I also recommend some time with knit 2 together and purl 2 together. Below you will find some helpful step by step pictures of what a dropped stitch looks like (My dad always says: "The first step to problem solving is recognizing the problem".), the approach and the finished product. The loop is the stitch from the row below and the ladder is the strand of yarn above the loop. Thread the ladder through the loop to fix your dropped stitch.
You want to approach a knit stitch from the knit side or front (side facing you) and pick up the loop and then pick up your ladder. Pull your ladder through the loop toward you. Place repaired stitch back on left needle and knit.
You want to approach a purl stitch from the purl side or the back side (side facing away from you) and pick up the ladder first then the loop. Pull the ladder through the loop away from you. Place repaired stitch back on left needle and purl.
Knit 2 together:
You will approach this the same as a knit stitch but there will be 2 loops and 1 ladder. With the knit side facing you, put your crochet hook into the left loop first then the right loop then pick up the ladder. Pull the ladder through both loops toward you and place on left needle. Knit the stitch.
Purl 2 together:
You will approach this the same as a purl stitch but there will be 2 loops and 1 ladder. With the purl side facing away from you, put your crochet hook through the ladder first, next the right loop first then the left loop. Pull the ladder through both loops and put the stitch on your left needle and purl
Practice all of the above until you feel comfortable. Picking up stitches will become easy and a no brainer with time.