If you go to an MD school, and you want a competitive residency, you do this:
1. Get excellent grades in preclinical years
2. Get an excellent USMLE step 1 board score
3. Publish research
4. Get excellent evaluations from the dean and your profs (and/or LORs)
5. Get honors in as many 3rd year rotations as possible
6. Get excellent USMLE step 2 scores (two exams)
7. Do at least 2 audition rotations, during 4th year, at residency programs in which you're interested, and make a strong positive impression
8. Organize your 4th year so that you can easily get away for residency interviews in October-January, and push any required 4th year rotations out to the end of the year
9. Apply to one or more match programs for ACGME/"MD" residencies (not all residencies use the same match).
If you go to a DO school, and you want to pursue a competitive ACGME/"MD" residency, you do all of the above, with the following points of interest:
1. You have to take the COMLEX exams in addition to the USMLE exams. Passing the COMLEX exams is a requirement for DO graduation and licensing. The COMLEX tests OPP, and the USMLE has more biochem, so it's not quite two-birds-one-stone.
2. You have to do some work to get your 4th year scheduled favorably. DO schools typically have lots of 4th year electives (to be used for auditions), but there are also lots of 4th year required rotations, and you may be up against a lottery to get your electives when you need them. You have to complete your 3rd year rotations to be eligible for auditions, and auditions need to be done as early in 4th year as possible, and you need to be free for interviews Oct-Jan. If you get scheduled to do a 4 month rural FM rotation from July - Oct, you're screwed.
3. You have to bypass the AOA/DO match. If you participate in the AOA/DO match, and you are matched in an AOA/DO residency, you're contractually bound to go.
4. You have to think about where you're going to practice, and whether you're required to do a traditional AOA/DO rotating internship. To be licensed to practice by the osteopathic board in 5 states (FL, WV, MI, PA, OK) you are required to use your intern year in an AOA/DO internship, which might start the clock on your residency, which might mean you're out of training funds a year early. There's a Rule 42 exception you can file with the AOA to bypass the traditional requirement, and 99% of these are approved. You can find combined AOA/ACGME residencies where the first year is approved by the AOA, but not typically with competitive ACGME programs.
5. In competing for an ACGME residency, you will run into residency program directors who still believe that DOs are poorly trained, and the interview/match process will expose DO stigma. So the more educated you can be about which residencies have already had DOs, or have DO faculty, etc., the more likely you are to succeed. This starts being relevant during 3rd year when you start pursuing auditions - don't waste an audition at a program that isn't going to interview you.
Also:
1. If you go to an MD school you aren't eligible for AOA/DO residencies.
2. If you go to a DO school and you want to do an ACGME primary care residency, you might not have to take the USMLE, and you might not have to do auditions, depending on the ACGME residency's history with DOs.
3. If you go to a DO school and you want to do a competitive DO residency (like ortho), you don't have to worry about the USMLE, but you still need to do auditions with DO ortho programs.
Highly recommended reading:
Iserson's Getting into a Residency.
Obviously I learned all this stuff because I'm going DO and interested in competitive ACGME residencies, but caveat emptor - I'm still just a premed.
Best of luck to you.