Tips for a teenager looking to get their first job?

So I've been applying to a lot of places in my town, and getting denied a lot. I have a cover letter and a resume that I've made and had help with from other people in my life. I just can't seem to find a job though, and I have no prior job experience which makes it difficult to even get an interview. I've been denied 3 times in the past 4 days, and one of those times was only 3 minutes after I submitted my application. Any tips to improve my job search and increase my chances of getting a position?