You reject any vegetable that isn't yellow. You like basmati rice, but detest jasmine, Arborio, and brown. You dine at one restaurant, and you always order the same meal. You are a finicky eater — that is, you are quite particular about food.
Fastidious, fussy, picky, persnickety: these are all synonyms for finicky, and they all suggest someone with extremely exacting tastes and habits, someone almost impossible to please. Finicky can also be used to describe something that demands a great deal of care and attention to detail — a finicky lock might require that you jiggle the key just so. Finicky generally conveys the sense that the person or thing it describes is quirky and pointlessly precise.