What are the laws of exponent when multiplying monomials?

When multiplying monomials, the exponent rules depends on its placement. For example, (3x)^2 would be 9(x^2). However, 3x^2 is simply 3(x^2). (xy)^2 means you have to use the F.O.I.L. method, meaning x*x + x*y + y*y, or x^2 + xy + y^2.