Some beginners are taught to slip the first stitch of every row, if they find the edges loose and uneven. Edge stitches are referred to as the selvages of the knit fabric, and are often one or two stitches at each end. It is important to note that selvage stitches are added to the total stitch count, and are used to stabilize the knit and prepare it for seaming, or to finish the edge.
I would suggest not slipping the stitch, but practice this simple tip to create an even side edge. I simply make sure when I knit or purl the first stitch, that I pull the yarn tighter than the rest of the row. If all else fails, this method works well, creating a chain along the edge of stockinette stitch. Row 1 (right side): Slip the first stitch knitwise, work to the last stitch, knit one. Row 2: Slip the first stitch purlwise, work to the last stitch, purl one. This method is only one of many variations to create a selvage edge, and remember if you want to include a selvage, add these extra stitches to the total stitch count.