に限る expresses a strong personal preference or judgment that a particular action or thing is the best choice, with no alternative being better. It is often used in casual, spoken Japanese, and less in formal writing. You can use it to say what you think is the best way to do something or what is most desirable in a situation. It often carries a nuance of 'there's nothing better than this' and can sound a bit subjective. When used with a verb, it attaches to the dictionary form, as in 行くに限る. When used with a noun, it often follows the noun directly, as in 旅行に限る, but you also see に限る after a noun that is the subject of a comparison, like 夏はビールに限る. Note that you cannot use it with past tense or negative forms; it is always present tense. In conversation, you might hear it with a falling intonation to emphasize the opinion.