Tension of stitches on the needle
I've done some knitting and ripping this week while re-learning to knit again. I watched some very helpful on-line videos. I'm having a problem making the stitches too tight which makes it difficult to insert a needle. While watching the videos I noticed that the knitter doesn't tug much on the stitch as she transfers it to the other needle; she just simply keeps the tips of the needles close and transfers the stitch and then begins the next one.
What is the basic principle of determining the tension of a stitch on the needle? How much should I tug on the yarn to snug it up, if at all?
Currently I'm just practicing the basics but my first projects will be scarves and dishcloths.