I want to break 17:30 this year in a 5k. Any tips?

Last season I ran an 18:52 PR during my first season of XC, and this season I want to do a lot better. This track season I ran a 5:01 mile. My school's XC team is incredibly competitive, and this year a 17:30 PR is likely to not even make Varsity. I need training tips for this summer to put me ahead of the other runners. I am already doing long runs of 5-8 miles daily, but I feel as if I might need to focus more on 400-1000m repeats. I have just about any terrain at my disposal if that helps at all. Thanks a lot!