This can vary, it really can be however big or small you like, but I generally do 4x4 or 5x5.
-How many chains shall I do for a *single/double/etc' blanket?
Again, this can vary. I would suggest that you do your chain and lay it down agains the bed you are wanting it for. It should be the same width. You should then ad a few more to make it a little wider.
-How much yarn do I need?
Unfortunately, I will be able to answer individuals questions about how much yarn you would used do to multiple factors effecting it. Such as, your tension, the size of hook and the yarn being used.
-What camera do you use?
I use a Panasonic Lumix GF1 to film my videos on a tripod.
-What do you do for a living?
My full time job is a full time Beauty Therapy Lecturer at a College