Thanks to everyone who has replied...especially suzeeq and fibrenut...I think I was trying to reverse stitches and getting confused whether I started the row with knit or purl. I know it takes more than two rows; I had done five or six rows and my ribbing was not looking right.
Purl the purl stitches and knit the knit stitches, as the work is facing you. So I don't have to remember which row I'm on after the first two, I can just do whichever stitch I'm looking at on the previous row. I will give that a try and see if it turns out looking better.