The two things that I know I would like to get on top of: find the perfect alchemy between good product (production, cohesion, price point) and a good knowledge of technology (quality pictures, descriptions, marketing...)...
... speaking of which, I'm off to read up on SEO. I tried to figure it out (once) but I still don't get it. I'm really missing a trick here, I hope I'll make more sense of it through your top tip number 6 !!!