HNS-CASPER is a helpful mnemonic for getting through a patient assessment. It's something I learned 20+ years ago and still find it helpful today. It was designed to help us remember the pieces and parts of a physical assessment and generally the order it should be done. There is one element of it that gets debated in terms of what order it should be done, but I'll get to that. First, the mnemonic:

1. (H) stands for Head. This will include DCAP-BTLS, looking for "raccoon eyes," "battle signs," blood from ears, mouth or nose, pupils being equal and reactive to light (PEARL), airway, and skin and eye color. When I find blood coming from the ears or nose, I also like to perform the Halo test. 
2. (N) stands for Neck. This will include palpating C-Spine, checking for JVD, that the trachea is midline (or not) and DCAP-BTLS. 
3. (S) stands for Shoulders. This will include checking for stability of the shoulder girdle, crepitus, and DCAP-BTLS. 
4. (C) stands for Chest. This includes checking for medical alert tags, checking for equal rise and fall of the chest, breath rhythm, equal or paradoxical chest movement, stability of the rib cage, DCAP-BTLS, crepitus, skin color, and auscultating (listening) for heart ad lung sounds. 
5. (A) stands for Abdomen. This includes looking, listening and feeling all four quadrants. You're looking for the usual DCAP-BTLS items, but also for point tenderness, rebound tenderness, referred or radiating pain on palpation, bulging/pulsing masses, rigidity, and level of activity of bowel sounds. 
6. (S) in this case stands for Spine. It debatable whether you want to roll the patient at this point in your exam or later, but it is important at some point in your exam to examine the spinal area of your patient. You will want to assure appropriate C-Spine precautions before moving any patient. Then you'll be looking and feeling for the usual DCAP-BTLS items, including exit woulds from gunshots. You may notice obvious deformities in the spine from a fall or medical condition. You may have bleeding or additional wounds in the posterior as well. Be sure to check the buttocks during this step as well. 
7. (P) stands for Pelvis. With your patient lying on his/her back again, you'll check for stability of the pelvis, crepitus, pain (pain, if present, can be severe in the case of a pelvic fracture), and DCAP-BTLS items. Priapism (a penile erection) in a trauma patient may be a sign of a fracture of the C-7 vertebrate. This condition should be noted and appropriate c-spine precautions verified. 
8. (E) stands for Extremities. In the primary exam, this can be a simple look and feel exercise - sweep for obvious blood, check for medical alert tags, look for DCAP-BTLS items. During secondary exam, this may include additional items like skin turgor, checks for track marks (a sign that you may be dealing with a drug user), skin color and temperature, rechecking capillary refill, clubbed finger nails, black lines in the finger nails, etc. Any unusual findings will help medical providers down the line to identify possible underlying medical conditions and adjust treatment accordingly. 
9. (R) stands for two things that way I was taught: Reflexes and Recheck Vital Signs. First, you want to do your neurological exam. Can the patient "press the gas pedal" with both feet? Can they lift with their toes against your hands? Can they squeeze your two fingers? What is the strength? Is it equal on both sides? Do they know which finger or toe you are touching? Next, you want to remind yourself that you need to go back and check your vital signs again after the secondary exam. Rechecking vital signs gives you a trend. Is the patient improving or getting worse? How will you adjust your treatment?

If you can complete these nine focus areas, you will have conducted a pretty thorough physical exam. Just remember that the initial "Rapid Trauma" exam is just that - rapid. I can get one done in about 60 seconds. Sweep and go, keeping an eye out for breathing problems, severe bleeding and/or shock.

Take vital signs after the rapid assessment as your baseline (unless you're in a mass casualty situation and conducting rapid triage), then return to do your secondary assessment when you have more time. I typically did my secondary assessment on more stable patients while en-route to a medical facility - time permitting (which was most of the time).