I can answer some of your questions:
1) What is a 'good' length to start dreads?
My hair was a boob length when I started and has since shrunk up a bit to just passed my shoulders. You only need a few inches of length to start but be prepared for some shrinkage. They will begin to grow again though.
2) What do you do ,regularly, get keep your dreads up?
I began mine with the crochet method which makes them look quite tight and good at first....