If you plan to match with a spouse, significant other, or friend you will take part in the NRMP Couples Match. Applicants matching through the Couples Match have close to the same match rate as those participating in the regular Match. There is no place for you to indicate you are couple matching on residency applications, so be sure to state it clearly in your personal statement, and during your interviews. Most applicants who participate in the Couples Match also like to interview for their residency programs at the same time. This is not difficult to do if you submit your program applications early.
Early applicants receive early interview invitations and that means more choice of interview dates.
Also be sure to investigate how flexible programs are about scheduling on-call and vacation time. You could very easily find yourself spending very little time with your partner if you cannot schedule time together. Finally, each partner can enter up to 15 programs without paying additional fees, but a couple's ROL may have more than 15 listings because you are allowed to pair each partner's choice of programs in any combination. Theoretically, if each partner listed 15 different programs and the couple listed every combination of those programs on their ROL, they would have 225 pairs of programs on their ROLs. Worksheets and more details about couple matching is in the 2000 NRMP Handbook for Students, available in the Office of Student Affairs in June.