I read this recently about the importance of dialogue.

Dialogue tells us what people say and it hints at what they do not. It encourages readers to bring a book to life by enticing their participation in it. They then supply their own reading of how loudly or softly, truly or falsely, words are exchanged. When a writer allows his characters to talk among themselves, he grants them their freedom. If only because the subconscious can then chime in, his premeditated scheme never wholly dictates what someone will say.

Dialogue in a novel is like stained glass, the surrounding prose is there to frame and support it.

Well said. Now here is an author named Tony Jordan with some advice on writing dialogue.