In the Book of Mormon, book of Moroni, chapter seven, verse 19 (Moroni 7:19), we read: “Wherefore, I beseech of you, brethren, that ye should search diligently in the light of Christ that ye may know good from evil; and if ye will lay hold upon every good thing, and condemn it not, ye certainly will be a child of Christ.”
Start by choosing the right, and you won’t be able to choose poorly without being prompted to return to the path, or warned not to get off, but also, if you know you’re on the right path and stay on the right path for long, you will be able to see/feel the difference between what is right and what is wrong... you’ll be able to see what else/who else is similar to that from which you started—it becomes your “standard” to judge from!
JPS