To keep your edges of your knitting smooth, if the pattern allows for it, slip the first stitch of every row. This means, if you are right handed, that you would transfer the first stitch from your left needle to your right needle without knitting or purling it, and then work the remainder of your row in whatever stitch or pattern as called for in your instructions.
What this in effect does is reduce the amount of yarn used at the end stitch, keeping your work a bit tighter and tidier. Newer knitters often have difficulty with tension in their knitting until they become comfortable enough to get a good smooth rhythm going while they work, and this can often be most apparent in the edges.
The other benefit to slipping that first stitch, particularly for newer knitters, is it can make it easier if you have to go back in later on and sew two edges together, since you will have clearly demarked rows to work with. To the right is a picture of garter stitch worked with a slipped stitch at the beginning of each row. On the other hand, more experienced knitters, whose work (and tension) has become more uniform, may prefer not to slip that first stitch. When assembling a garment, such as setting in the sleeve of a sweater, you will have a nice, tight and even “ladder” to work with when joining pieces with mattress stitch.
Having said all this, if you are working on something using a fuzzy novelty multicolor yarn, no one will ever know the difference if you do or don’t slip that first stitch. However, it’s not a bad habit to learn and store away in your “knitting muscle memory”.