A pillow cover is a great project, even for a beginner. Woven fabrics with little stretch are the easiest to use. Your local craft store has patterns to assist you with a design. To develop your own designs, take careful measurements and provide for seam allowances.
Choose a firm fabric. Mark the fabric to cut so that any pattern is centered. Stitch around all but one side, turn, press, insert pillow and hand stitch the opening.