Rule 1. Use effect when you mean bring about or brought about, cause or caused.

Example He effected a commotion in the crowd.

Rule 2. Use effect when you mean result.

Example What effect did that speech have?

Rule 3. Also use effect whenever any of these words precede it: a, an, the, no, any, take, into.

NOTE: These words may be separated from effect by an adjective.

Examples That book had a long-lasting effect on my thinking.
Has the medicine produced any noticeable effects?

Rule 4. If none of the above fit, use affect.