Getting some balayage, got some Q’s. ✌🏼

Hi! I am going to see my hair dresser on Wednesday. I’ve only ever gotten blonde highlights once before many years ago. I now have natural dark brown hair and am getting blonde balayage and a cut. Should I wash my hair tonight or tomorrow night? (Is it better to have day old hair before a color?) Whats the best shampoo/conditioner to buy for color treated hair? What heat protectant do you use? Thanks for taking the time! 😘😘😘✌🏼