Studying music at the university level is an amazing experience, but many potential students are taken by surprise by the admission process. If you're considering music school, there are some realities you should be aware of when making the choice to audition.
Most music schools will charge an audition fee of $25-100 and will not schedule your audition until they receive it. Also, walking into an audition with photocopies of your music is considered bad form, so plan on buying originals of everything you intend to play. Travel will add to your total cost as well; depending on how far away you're looking, you might have plane tickets, hotel reservations, and rental cars to add to your list of expenses.
The audition season lasts from December through March, so audition prep should ideally start no later than the summer before you intend to apply for college. I tell my college prep students that they should be practicing 2-3 hours a day minimum. Your audition music should be completely ingrained, as the audition experience is nerve-wracking enough even if you're fully prepared. This might (and probably will) mean that other activities take a backseat during audition prep.
Available Studio Spaces
Due to the popularity of the flute, there are usually many more applicants than spaces on a teacher's roster. At particularly elite music schools or conservatories, even students who are qualified for admission might not get in simply due to lack of space. A great way to set yourself apart from the pack is to contact the teacher you want to study with and ask for a trial lesson. Do this before audition season gets underway, ideally in September or October. Tell them you're auditioning for admission and that you'd like to get to know them if they have time in their schedule.
Streamline your repertoire list as much as possible. Most schools will have similar audition rep requirements, so try to pick pieces that you can use for more than one of your potential schools. For example, if all your schools require a Bach sonata, but only one specifically requires the B minor sonata, use the B minor for all your auditions. Make sure you read each school's requirements carefully. There's nothing worse than being asked to play something you haven't prepared, especially if the school gave a specific list of required pieces.
Most schools will require music theory, ear training (sometimes called aural theory or aural skills), and history entrance exams. For some schools, these are simply to place you in the correct level of class once you're admitted, but for others, admission is contingent on passing the exams. Either way, include some basic theory and history in your audition prep plan. Teoria is a great online resource for learning theory and ear training. Teach Me About Music has basic overviews and self-tests for each period in Western music history.
If you take these things into account and make getting into music school your top priority, you will greatly increase your chances of getting into your school of choice.