Custom Fields On Product Set Up Page?

[minson]

I am adding products to my site.

I need to be able to have my shoppers fill in additional info about certain products before adding the item to their cart.

I need to know the existing brand of their item, what type of product they currently use (this one is checkbox filed), size of existing item, manufacturer and part number of existing item, etc.

How do I go about adding these choices?

Also, we have a nearly endless supply of product, so I don't want to use the product quantity/units in stock feature. Where do I turn that off?

Thank you!