Starting my own business (the legalities of it)?

Hi I was wondering if anyone had any pointers on how I should go about creating my own pet bakery. More the business side of it I have no clue how to go about getting the permit or at what point it is required I have one as well as taxing my items - if I sell under a certain amount do I put tax on or is it only after say I've made at least 50.00 is it no longer a hobby. This is something I'm very pionate about also if i plan to donate 5-10% of my sells to the humane society do I need to put that on taxes at the end of the year or how do I go about it. As you can tell I'm pretty much in the dark as far as the technical law - side of this goes, I just really want to start off right and not get in trouble later on out of pure ignorance so any insight from someone who deals with business or has started a similar one would be of much help!