I am often asked how can someone best prepare to go straight through/avoid a gap year. I'll be totally transparent and tell you that I am a big fan of the gap year. In fact, I think the gap year is actually more common than going straight through. There are many, many benefits of a gap year.
Taking a gap year means that you would apply in May/June of your 4th year, so right around graduation. If you took a gap year, your schedule would like like this:
August/September after 3rd Year: Take MCAT/DAT
January of 4th Year: Begin Prepping Application
May of 4th Year: Open Application
June after 4th Year: Submit Application
July-August after Graduation: Submit Secondaries
October-July: Get Accepted
July-August, One year after graduating: Start School
Even though you "aren't doing anything" (as it's so lovingly stated to me), the year is a very hectic year. You should definitely be working or doing something to occupy yourself full time during your gap year, but don't discount how busy you might be writing secondaries, researching schools, preparing for interviews, attending fairs to network and staying in touch with schools. Once you get accepted, you have to negotiate financial aid packages and find housing and roommates. It's a lot for some people to move out of state.
What to do during your gap year?
First, you need to assess your application and identify any weaknesses. If you feel worried about your GPA, you should take more upper div science classes. If you plan to retake the MCAT, you should begin studying. Maybe you need to reinforce Chemistry, so you choose to take Chem over at a CC. Maybe you recognize that you haven't spent much time in a hospital, so rather than doing research, you apply for jobs like scribing or transporting so that you spend more time in the setting in which you hope to work one day. I hear a lot of people worry that they do not have enough clinical experience. If you don't have a license, it's not expected that you have real clinical experience. What people really mean is they haven't spent enough time with patients. That's easy. Apply for jobs in residential psychiatric facilities, become a CNA, or volunteer in a hospital.
Long story short, whatever you do in your gap year can start with whatever you think your biggest weakness is. If you don't think you have any weaknesses (totally possible), then do whatever you want. Some people use it to redefine themselves. They choose something completely outside the box so they can explore their skills and interests more.
Benefits of a Gap Year
You have your 4th year grades in your application
You have one more year of experiences to include
You have one more year to collect LOR
You have one more year to gain life perspective
Negatives to a Gap Year
I honestly do not see any negative to a gap year. Schools like older, mature applicants. The older you are, the better. The more years you take, the more success you'll see.
I know this isn't what everyone wants to hear. But like my title, I have no choice but to be honest with you.