I'm new to Dungeons and Dragons 3.5, and I'm having trouble figuring out what makes a feat either weak or strong.

This answer, for example, says that Combat Expertise, Dodge, Mobility, Spring Attack, Whirlwind Attack, and Weapon Focus are weak; that Improved Trip and Weapon Finesse are good for the right character build; and that Divine Metamagic, Leadership, Natural Spell, Quicken Spell are strong.

But I'd like to know how I can judge whether a feat is weak or strong.

For example, some handbooks rate feats as good or bad, but how do those handbooks' authors reach their conclusions? Is there an objective measure? Or is a feat's value completely dependent upon the character or the campaign?