If you'd prefer a commercially made worm farm, I would recommend Worm Swag , or The Can'O'Worms 2.
Chopped straw is great for helping aeration of the worm bin.
Only use about a cup of scraps to start with, then when that is nearly all gone add some more. Once the worms are used to the bin, you will soon be able to judge how much they are processing. Keep just ahead of them - when the worms move into the last lot of scraps, add some more. Don't overfeed the bin, as this can cause problems with smells and unwanted pests. This is the time to harvest your castings to use in your garden.