Email question - van't Hoff factor

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Can you please explain how to determine the i factor.  Now matter how much I read the book and look at examples I can't figure it out.  Thanks,
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There are a couple things that could be "the i factor", but I'll assume this question is about the van't Hoff factor that's used when determining changes due to colligative properties. Remember, colligative properties are properties of a solution that depend only upon the number of solute particle, not the identity of those solute particles. It doesn't matter if those solute particles are molecules, or cations, or anions, or a big random mixture of them all. When an ionic compound dissolves in water, it dissociates (at least somewhat) into its component ions. The number of ions (particles) that each formula unit breaks into when it dissolves is the van't Hoff factor. For example, if NaCl(s) is dissolved in water, it forms 1 Na⁺¹(aq) ion and 1 Cl^-1(aq) ion, so each formula unit (NaCl) forms 2 particles (ions) in solution; the van't Hoff factor is "2". For polyatomic ions, the ions don't break down into their individual atom, they stay polyatomic ions, so if K₂SO₄(s) is dissolved in water, it forms 2 K⁺¹(aq) ions and 1 SO₄^-2(aq) ion in solution; the van't Hoff factor is "3".