Disclaimer: Here's how it's done in my area. Check with your instructor.
Scene Safety, BSI, tell your pt not to move, c-spine, consent, evaluate ABCs, place the pt on supplemental oxygen at 15lpm via NRB.
Check the head for DCAP-BTLS. Also check for cerebrospinal fluid coming fro the ears or bleeding from the ears, nose, or mouth.
Check the neck for DCAP-BTLS. Also check for JVD and tracheal deviation. Once the neck is clear, apply a c-collar.
Check the chest for DCAP-BTLS. Also check for equal and symmetrical expansion, flail segments, and paradoxical movement. Check lung sounds (doesn't matter if you hear rales, etc., just make sure they're present).
Check the abdomen for DCAP-BTLS. Palpate for masses, distension, and rigidity.
Check the pelvis for DCAP-BTLS.
Check the lower extremities for DCAP-BTLS. Assess PMS.
Check the upper extremities for DCAP-BTLS. Assess PMS. If you really want to impress your proctor, check for a positive Babinski sign.
When your roll the patient to place them on a backboard, quickly check the back of the head, the back, and the buttocks for DCAP-BTLS. Also check lung sounds on the back.
If you have the luxury of a bystander, clear one of the patient's arms early so that your partner can pass c-spine off to said bystander and obtain vital signs while you complete your assessment.
Like writchey said, this is a TRAUMA assessment, not a MEDICAL assessment. Don't get caught up in things like percussing the abdomen, you'll just waste your time. It's called a RAPID trauma assessment. Minute details are what you have a detailed physical exam and ongoing assessment for.
Best of luck.