fine-tune

(verb) improve or perfect by pruning or polishing. Synonyms: polish, refine, down. Example: "Refine one's style of writing."

(verb) adjust finely. Synonyms: tweak. Example: "Fine-tune the engine."

(verb) make fine adjustments or divide into marked intervals for optimal measuring. Synonyms: calibrate, graduate. Examples: "Calibrate an instrument." "Graduate a cylinder."