Use commas to create off non-essential expressions–words, phrases, and clauses that are not necessary for the meaning or structure of the sentence. You can inform whether an expression is nonessential by trying to omit it. If the sentence is practical and is structurally right, the expression is non-essential and should be triggered by commas.

non-essential: Let’s talk to Bob, who has experience in this area.
Essential: Let’s talk to anyone who has experience in this region.