Tips for being on varsity xc next year?

i am going to be a freshman next year and going into my third year of cross country i would like to be on varsity last year i was the 11th best on the team with an 18:27 5k two varsity runners have graduated i just want tips on how to run a more tactical race in know about speed training but could you tell how many miles a should run a week im at 55 now