It can be confusing for a beginner who is staring at the CXR (chest x-ray) to figure out what is going on. Though, this usually requires a long term training, for medical students, a good mnemonic may be a good start.
image from life in the fast lane
Before you use any mnemoics to start the approach, always remember to check the quality of the CXR. 不管用什麼口訣的順序，首先要評估胸片質量。
1.ABCDEFGHI (this is a very detailed one, though may be harder to memorize)
Airway 氣道
Bones and soft tissues/Breast shadows 骨頭和軟組織、乳腺組織
Bones:symmetry, fractures, osteoporosis, and lesions.
Soft tissues: foreign bodies, swelling, and subcutaneous air.
Heart size: should be <50% of the chest diameter on PA films, <60% on AP films.
Check for the heart shape, calcifications, and prosthetic valves.
Check the hemidiaphragms for position (the right is commonly slightly higher than the left due to the liver) and shape (may be flattened bilaterally in chronic asthma or emphysema, or unilaterally in case of tension pneumothorax or foreign body aspiration).
Look below the diaphragm for free gas.
Also check the costophrenic angles for sharpness (blunted angles may indicate small effusions). And also check the lateral film for small posterior effusions.
Check lungs for infiltrates (interstitial vs. alveolar), masses, consolidation (+/- air bronchograms), pneumothoraces, and vascular markings. Vessels should taper and should be almost invisible at the lung periphery.
Evaluate the major and minor fissures for thickening, fluid or change in position.
Check position of foreign bodies e.g. ETT, NGT, pacemaker leads, central venous lines etc. Comment on previous surgery e.g. cholecystectomy clips, sternotomy wires.
Check aortic size and shape and the outlines of pulmonary vessels. The aortic knob should be clearly seen.
Evaluate the hila for lymphadenopathy, calcifications, and masses. The left hilum is normally higher than the right. Check for widening of the mediastinum (which may indicate aortic dissection in the appropriate clinical setting) and tracheal deviation (which may indicate a mass effect, e.g. from large goitre, or tension pneumothorax). In children, be careful not to mistake the thymus for a mass!
Synthesise all the findings together & act as a double check.
2. ABCEDF
Airway 氣道
Bones and soft tissues 骨和軟組織
Cardiac Silhouette (including large vessels, hila) 心臟區域（包括大血管、肺門等）
Diaphram and below (Below here means gastric bubbles and free gas)膈及以下（包括膈下游離氣體、胃腸內的氣體）
Effusion (including pnumothorax) 滲出（包括氣胸等）
Fields (including fisures, foreign body) 肺野（及肺裂、異物等）
3. ABCDE
Air: Central airways and lung parenchyma 氣體：氣道和肺實質
Bones: Ribs, clavicles, spine, shoulders,scapulae 骨：肋骨、鎖骨、脊椎骨、肩膀、肩胛骨
Cardiac: Heart, blood vessels andmediastinum 心臟部分：心臟、血管、縱膈
Diaphragm and pleura 膈和胸膜
Everything else: soft tissues of the neck,chest wall 其它
We mentioned you should always check the quality of CXR in the beginning,
use "PIER"（碼頭） to memorize this.
Position: PA film or AP film? 位置：後前位還是前後位？
Inspiration: Count the posterior ribs, should beable to see the 10th or 11th rib 吸氣：數一數背部肋骨，一般應該能看到十個或者十一個。
Exposure: If a good exposure, you should be ableto see behind the heart, the blood vessels andthe intervertebral spaces. 曝光情況：好的話，應該能看到心臟後面的結構，大血管和椎間隙。
Rotation: The clavicles should appear symmetric,equal in length and be equidistant from the spine.If there is rotation, the side farthest from the filmwill be narrower and whiter 旋轉：鎖骨大致對稱。
There are also many other similar mnemonics for the CXR approach, just go and search for one that is easy for you to memorize.