Make sure that the dialogue has purpose and lends strength to the scene. A well-told story is one that's a good blend of strong dialogue and strong narrative. If you’re not sure how strong your dialogue is, strip away everything but the dialogue, then read it and see how it holds up.
If everything of value---all the strength in the scene---is in words the characters don’t say, it's time to rework your dialogue. You know it's strong when removing a line of dialogue or a sentence of narrative has a negative impact on the scene. If you can remove it and the scene doesn't miss it, then you're probably repeating yourself or you're wasting words and space on things that don't matter, so go ahead and leave it out.
If writing dialogue doesn’t come naturally to you, don’t lose heart. It’s a skill and it can be learned if you’re willing to practice and put forth the effort you need to learn it.
“You don't "include dialogue" because dialogue is "good" or "not good." You write scenes because those are the most entertaining or important events, and you use dialogue because what matters is what the people say to each other. If you included meaningless dialogue -- for instance, conversation with a store clerk as your character buys gum, when that conversation leads exactly nowhere and the gum is never even chewed -- then it only makes your readers impatient for you to get on with the story (i.e., the things that are causally connected with the dilemmas they care about).”
As Card says, you write dialogue because what matters is what the people say to each other in the scenes your readers want to experience. Are you writing a scene in which your romance hero and heroine are learning key facts about one another? That dialogue is probably going to be important and should be included.
Is your heroine going to have to divulge a huge secret to the hero at some point in the book? Then don't have her revealing all the details of that secret to her mother, sister, or best friend before you reach that point. Save that important dialogue for when it's really important -- the scene when the hero is going to be forced to either love her anyway or turn his back on her. If the dialogue we read there is nothing more than a repeat of information we already know, your scene is going to lose most of the impact it could have had -- and that will cost you readers.
Be careful as you choose which scenes and conversations to show and which to summarize or skip. If you summarize or skip scenes that the readers really want to see, you end up losing them because you aren't satisfying their desire to see these people in action with each other. Resist the urge to let your romance hero and heroine indulge in countless scenes filled with witty banter. You may believe that you're building sexual tension and keeping your readers on the edge of their seats, but if the readers aren't learning new, vital information during each conversation, even the wittiest dialogue is going to fall flat on its face.
With dialogue, it's a common tendency to avoid the scenes our readers want most to read because we feel unequal to the task of writing it well enough. But there are no easy outs if you want to be successful at this. You must tackle the scenes you want to write the least because those are probably the ones you need to write most.
You must write the dialogue you’re most afraid of because it will probably -- if you persevere -- become the most powerful in your book.