Look at the work as if you are going to start the next row. If you see a bunch of flat v's then you knit that row, if it's a bunch of bumps then you purl. Think about stockinette this way, you are putting all the bumps on one side, so you want to keep the flat side flat and not add bumps, if you purl it puts the bumps on the side facing you, knitting puts them on the other side.
I hope this helps.
Oh and you don't need a row counter to keep track, before you start your next row slip a stitch counter (I use little hair ties) at the bottom of the needle then when ever you are working onto the needle you know to knit.