Fitness is important. Consider working with a trainer who works specifically with models.
Eat right. Contrary to what some people tell you, you should eat healthy foods, as well as healthy amounts of food. Veggies, fruits, whole grains, healthy fats, and proteins should make up the basics of your diet. Sugars, starches, empty carbohydrates, and unhealthy fats should be avoided as much as possible.
Be sure to drink a lot of water too because that can clear up acne too!
Focus on keeping your skin clear and glowing and your hair shiny and healthy.
Extra!!!! - Do not be shy. You will have to promote yourself and look for opportunities to step up and prove your abilities.
Standing back to seem “polite” will not get you where you are going. Be yourself, let your personality shine, and have a confident attitude. If you don't feel confident, fake it; modelling often requires acting skill as well!