The Basic Knit Bind off (or Cast off) is the most common way to finish a project and get it off your needles.
Step 1: Knit two stitches as normal.
Step 2: Slip the first stitch over the second stitch.
Step 3: Knit one.
Step 4: Slip stitch over the new stitch.
Rep this until you have one stitch on your needle.
When you have one stitch left, break (or cut) your yarn and pull tight.