You need to listen more.

Years ago I learned to shut up and listen more. Not to be insulting. But working on dialogue is a bear. To get it right, I started listening to conversations around me, not to eavesdrop, but to learn to do it right. I noticed that most people do no speak/talk in full sentences. Some use half-sentences, some nod their heads, some make a one-word curt reply. Some are funny, some sarcastic, some just full of hell. This is how I learned to write dialogue, and although I don't know if I've perfected it yet, I'm still trying. Mainly I learned from reading other writers' novels, that use of slang is good, too. For instance: if you have a drug dealer referring to cocaine, he might use the expression 'nose candy'. Whereas a police officer might use a totally different expression and an average person, still another. I had to learn the different expressions by purchasing books on the use of slang. While most readers might not understand these expressions, if you use them right: e.g. `drug dealer-nose candy', they'll pick it up.

As well, you need to use dialogue in keeping with your characters. Never have a person who appears poorly educated speaking like a Rhodes Scholar UNLESS that is part of their basic personality and, for some reason known only to them, they're hiding their education. Be aware of your character's normal dialogue or you come off sounding ridiculous.

Another thing I noticed was that if an author wrote about someone with a heavy foreign accent, they would describe the person's accent. "He said with a heavy Italian accent." Then they would write the dialogue, not in that accent, but in plain English. And believe it or not, as you read, you heard the accent. Don't ask me how it works, but your mind works along with the author's suggestion of an accent. This was an excellent method because sometimes author's try imitating their idea of how that accent would sound and write it that way. As a result, reader's are turned off if it's not presented clearly enough. It has to be done in such a way that it's not confusing. I like the idea of a suggestion alone, and writing it properly. Let your readers' minds do the work

The same applies to narrative, which is mainly used for descriptions--characters, settings, locations, action taking place and so on. Don't use long, drawn out descriptions. They're boring and break the flow of the novel. Try to use more adjectives in describing things so that the picture of your description is clearly painted in readers' minds. To coin an oft used phrase, for example, 'his mouth was a tightened wound', meaning he was angry. Or, 'her face was screwed up with disgust'. While these might be poor examples, they do make a point. Readers do not want page after page of description in narrative. They want to get on with the story. Sometimes it's better if you describe a character or setting over several pages. Once you give an idea of build, the second time the character appears, you give an idea of eye and hair color. 'Her dark eyes flashed hotly. She swiped a wisp of brown hair off her shoulders'. Or something like that. Do the same with descriptions of settings. Wait for the right moment to describe say furniture. 'The couch was plush, vivid red. When he sat, he seemed to sink into it'.

Novels should flow, not be dragged down with the use of overdone dialogue and narrative. And in answer to a question I've often been asked, yes, I do use slang in my narrative if it applies to the situation at hand.

If you have any questions, just post them in my remarks section and I'll answer as quickly as I can.