This description of nomenclature is intended as an introduction to the topic for general chemistry students. Please note that major simplifications have been made.
To name compounds you have to identify a compound as

Ionic Compound
•Ionic compounds are made from a metal and a nonmetal.

Covalent Compound
•Covalent compounds are made from two nonmetals.

Acid
•Acids are made from H⁺ and an anion. The anion may or may not be polyatomic.

Naming a covalent compound or an acid is straight forward, but once you have identified that a compound is ionic you have to determine if the cation is a type I or a type II cation.

For example, FeCl₃...

Is iron type I (no Roman numerals are needed) or type II (Roman numerals required) ?

All the cations made from Group 1 and 2 elements can only have a single charge; thus, they are type I cations.

As far as we are concerned, four of the transition metal cations are type I, Al³⁺ (Al is not actually a transition metal), Ag⁺, Zn²⁺, Cd²⁺, and all of the remaining transition metals and P block metal cations are type II.

Iron is a transition metal; thus, it is a type II cation.

What is the charge on the iron cation?

All compounds will be neutral, so the charge of the cation(s) must equal the charge of the anion(s).

Determine the charge of the anion. For monoatomic anions use the periodic table. For polyatomic ioncs you have to remember the charge.

Chloride is Cl^-.

There are 3 Cl's. Each Cl is -1 for a total of -3. Therefore, the Fe must be +3.

 Example, Cu(NO₃)₂...

Cu is a type II cation.

Each nitrate is -1 for a total of -2; therefore, the Cu must be +2.