Why would I/we enter the couples match?
Generally, because you are married or close enough. Any two people can enter the NRMP match as a couple, which will tie your residencies together by whatever rubric you choose. This is usually done in order to end up in the same geographic location, which can be defined as tightly (Manhattan) or as loosely (the Midwest) as suits your needs and circumstances:
Couples generally choose very close (city), friends occasionally choose relatively close (area), and mortal enemies choose distance (opposite coasts).
On the whole, couples do relatively well in the match (91.6% of partners match together and at least one partner matched in 94.6% in 2012 according to the NRMP), barely different from that of singletons (95%). That said, your advisor will recommend that you increase the number of programs you apply and interview at accordingly. The more difficult the field you enter, the harder it is to couples match (per conventional wisdom). Double pediatrics is easier than pediatrics/radiology, which in turn is easier than radiology/dermatology.
The overall process itself is simple: you check an extra box on ERAS to inform programs and check another box (and pay an extra $15) for the NRMP to register, then submit your ROL (rank order list) together. You enter it exactly as you want it. If you want prestige over closeness for your dream program, you can do that (though your relationship might not survive it!)
There is no couples match for the early match specialties, although, if applicable, all preliminary years are part of the NRMP and eligible for the couples match. That means that if one or more partners is entering ophthalmology or urology, there is no way to guarantee being together during residency, end stop. There can be informal agreements and all sorts of hand-shaking, but no formal system will help you or preserve your sanity. Historically, ENT, neurosurgery, and pediatric neurology were also early match, but that is no longer the case.
All residencies requiring a preliminary year can also be tough. These include radiology, ophthalmology, radiation oncology, dermatology, as well as some neurology, rehab, and anesthesia. There are some programs in these fields that are categorical (meaning that they include the internship year), in which case you will match normally. But anyone entering an advanced field will couples match that advanced field with their partner’s program. The prelim year is not and cannot be part of the couples match itself (except for early match advanced fields). This means you cannot guarantee being in the same location for internship (but you can maximize your chances by attempting to go to locales or programs with large or multiple preliminary programs or be willing to enter a preliminary surgery year). If you want to ensure being together during intern year, then prepare for a large number of preliminary and transitional interviews and increased application/interview costs.
How to approach the process as a couple
It is advisable to let programs know you are couples matching. This can be done on ERAS directly. You can also touch on this in your personal statement if it flows. This encourages PDs in different specialties at the same institution to talk and can result in interviews for one applicant that they may not have otherwise received.
You will bring it up briefly during every interview (you’d be surprised how often programs can forget).
It is generally easier to focus on areas that have a sufficient number of options to make matching likely. This in part varies on which fields you will pursue, but larger cities like NYC, Chicago, Boston, etc. tend to work well for increasing the number of permutations. It’s also generally easy to get a larger number of interviews in your geographical region.
For couples with one partner in the Early Match, it is worth it to keep in contact with programs once the spouse knows where they have matched in order to stress that you are specifically vying for a particular area/program.
It is okay to politely inquire as to application status when one partner has received interviews from an institution but the other has not heard back, especially in areas with only one institution. Some fields send invitations significantly earlier than others. Most programs understand that one spouse will have little interest in attending an interview only to find out their significant other has been rejected. It’s a wasted interview from both sides of the table.
Always be polite, but don’t be too hesitant to contact when it will change your plans. If a program isn’t responsive or accommodating at this stage in a game, that’s something to keep in mind. I was surprised at how accommodating programs were when contacted, even very early in the season.
Most couples prefer to travel together when possible in order to explore new cities, save on travel costs, etc. The success for this is highly variable and depends largely on both programs’ schedules and the pushiness of applicants in attempting to ascertain interviews and reschedule when possible. Programs generally are sympathetic to the plight of the couple.
Finally, the NRMP provides some excellent information and sample couples match rank-order lists (ROL).