Start with global vertical metrics
Units per em defines the design scale. Ascender, descender, and baseline guides show where typical forms sit, but individual marks and conjuncts may extend beyond them.
Treat spacing as part of the glyph
Advance width controls the cursor movement after a glyph. Left and right side bearings describe the space around its bounds. Inspect words and clusters, not isolated shapes alone.
Use snapping carefully
Grid and guide snapping improve consistency, but excessive snapping can flatten curves. Check filled and outline views at several sizes before marking a glyph complete.