particular — of or relating to a single or specific person, thing, group, class, occasion, etc., rather than to others or all; special rather than general: one's particular interests in books.
picky — extremely fussy or finicky, usually over trifles.
finicky — excessively particular or fastidious; difficult to please; fussy.
choosy — Someone who is choosy is difficult to please because they will only accept something if it is exactly what they want or if it is of very high quality.
critical — If a person is critical or in a critical condition in hospital, they are seriously ill.
fastidious — excessively particular, critical, or demanding; hard to please: a fastidious eater.
fussy — excessively busy with trifles; anxious or particular about petty details.
meticulous — taking or showing extreme care about minute details; precise; thorough: a meticulous craftsman; meticulous personal appearance.
niggling — petty; trivial; inconsequential: to quibble about a niggling difference in terminology.
nitpicking — to be excessively concerned with or critical of inconsequential details.
in particular — of or relating to a single or specific person, thing, group, class, occasion, etc., rather than to others or all; special rather than general: one's particular interests in books.