This is an issue that will puzzle you, because the rules don't always fit the phrases we use. However, use 'very well' for when someone/something DOES something. 'The dog runs very well.'
Use 'very good' for describing a noun. 'Your hair looks very good.' But, you will say, doesn't 'very good' refer to 'looks'? No, here refers to the hair. Take words like looks, is, have as words where your focus is the noun. Hope that helps!!:)