How to Knit: Stockinette Stitch

St st = Stockinette stitch

To figure out whether you should be knitting the row or purling the row, put your work in your left hand. 

Knit Side vs Purl Side Illustration

Which side is facing you? 

If the V's are facing you, you are on the knit side and should knit the row. If the bumps are facing you, you are on the purl side, so purl the row.