I have a feeling that when I move my yarn foward (or back) to change from a knit to a purl (and vice versa) that I am either pulling too tight or making it too loose – it is puckering…any ideas? 
Be sure that you are moving the yarn to the front and to the back up and BETWEEN the needles, not underneath everything. That’s what I did when I started learning ribbing and it puckered like crazy. That’s when I figured something must not be right!
hmmmmmm i’ll take another look at the videos on this site. i bought the CDs thinking i would be able to play them on my TV at home - but unfortunatley I can’t so i have to use my work computer…ugh