I *know* someone else has suggested this tip somewhere but I couldn't find it so I'll post it here. Sorry for the redundancy!
I've recently started using leftover scraps of pattern tissue as a starter and stabilizer for knits. I place the tissue on top of the seam, extending maybe 1/2" before the start of the seam. I start sewing right before the beginning of the seam and voila, the knit doesn't get eaten by the feed dogs.
The tissue paper also acts to reduce drag between the knit and the pressor foot. This really helps to feed the layers evenly. I've also used the paper to act as a "slip" between the feed dogs and clear elastic--so that the clear elastic doesn't drag along the dogs.