Determine Formal Charge

[Leslie Almaraz 4G]

How do you determine which element is better to have a formal charge in a compound?

[Vanessa Chuang 4F]

Regardless of the fact that a formal charge might be zero, all elements in a compound have formal charges. As long as an element is sharing bonds with another element, it will have some variation of a formal charge.
However, if you are asking about how you know which element should have a negative or positive charge if it is not possible to give it a zero formal charge, then the rule is that the more electronegative element should have the negative formal charge. Conversely, the less electronegative one should have the positive formal charge.

[mayarivers3I]

The element that should have the negative formal charge is the most electronegative element.

[PriscillaLi_3G]

You should give the negative formal charge to the most electronegative element because they want the electron to complete their shells and become more stable.