As you'll hear many times, the US programs regard US letters of recommendation as superior to the ones attained at foreign institutions. Whether you like it or not this means you need to get excellent/fabulous/amazing letters of recommendation. Do not mistake the fact that you are coming from an underdog position as a foreign graduate and that you need to wow them and not the other way around. That means coming in on weekends, holidays, staying late and doing more then they expect. Common sense that leads to excellent recommendations.
With regards to the technical details, letters of recommendation from rotations done under a foreign school are usually forwarded automatically from the schools office to the ECFMG and then to ERAS.
However, letters of recommendation received in the US must be sent in directly using special forms or addressed to the foreign school's US office which forwards the letters to the ECFMG and then to ERAS. Since the exact procedure on how to send in letters of recommendation changes frequently and depends on your school, your status as an FMG or IMG, and ECFMG policy we cannot provide you exact details on this issue. The best advice with is to check out exactly what has been done in previous years at your school as well as the ERAS and ECFMG policies on this issue during the specific year you will be applying.
With regards to timing, you want to try to get the letters from your first two electives. That way you can complete your application as soon as possible and increase the chances of someone starting to review it. With that in mind, its no big deal if the letters of recommendation come in a bit after you sent in your application; you can't always control the letter writer's schedule...
Residency Letters of Recommendadtion
Application & Interviews