Medicals.
Well you can start but do like the cervical check, Blood work like HIV test, Hep B, Syphilis, and hemoglobin first. Also, immunizations (i.e Polio, Varicella, Yellow Fever, Tetanus and etc). I saved the dental and vision for last.
I did all my medical exams before I even received the call so it can be done. You would just go back and have the doctors fill out the forms, sign and stamp it.