Contacting the institutions that you are interested in is a great place to start. If you are interested in UW or Cleveland Clinic, look over the information they make available over the web but if your questions remain unanswered, feel free to contact them. Talking to current residents (preferably graduates of foreign medical schools) at these programs can also be very helpful. They may share their background with you and have some insight into what their residency programs are looking for in their IMG applicants. Once you have a better idea of what they are looking for, you can plan accordingly, especially since you have considerable time before you apply for residency training.
While observerships are not hands on, the attending can still assess your fund of knowledge, how you carry yourself, etc. These are important things that your attending can comment on in a letter of recommendation for the residency application. A strong letter of recommendation may open up other doors - perhaps an opportunity for you to do more than just observe. A phone call on your behalf from an attending might get you an interview at one of the programs you desire. Don't underestimate the importance of connections. Best of luck.
Samir Desai, MD