Every item, and how it fit
Save the size on the label (S/M/L, W31 L30, 27 cm, US 9.5 and more) and the brand. Overall fit is one of three: fits well, some issues, or doesn't fit.
Rate each part — waist, length, sleeves, chest, shoe width and more — as tight / just right / loose, or short / just right / long.
You can also note the garment's measurements (length, chest, waist, inseam and more), with diagrams showing how to measure. Add up to two photos per item (the size tag and the whole piece), plus notes and the product page URL.