Why is my cat throwing up and how do i stop it?

every morning my cat is throwing up. i think it is the combination of him eating too much wet food and not enough dry food and also hair balls. how do i help prevent my cat from having hair balls or help my cat pass the hairballs through his poop and not throw it up? and should i start mixing his wet food with the dry food so he can eat both at the same time or keep the foods in separate bowls like i have been doing??