Dialogue shouldn't be the pain in the butt some people think it is. After all, we hear people talking all day every day, and we know our spoken language better than anyone. Once you know your characters and your voice for narration, dialogue should be a doddle.
The thing most writers struggle with is making dialogue sound natural. I must confess, dialogue was the first thing I truly nailed when I first started writing, but I think that's because I write in a very casual sort of way. If you can spin the most detailed and beautiful description, I'm guessing dialogue was more difficult to grasp. Something I've realised over the years is that people who 'get' description first struggle with dialogue and vice versa. They're two entirely different skills.
In your first draft, you should just go for it. Type your dialogue as fast as you can and have the characters' conversations out loud so you can hear them. I find that if something's not quite working, I'll never pick it out reading in my head. You must read dialogue out loud to understand it. When you read aloud, you notice that no one says can not anymore. Everyone says can't. In my novels, I go as far as wanna instead of want to with some characters.
It may make you cringe, but some characters won't use words correctly, and they won't speak in perfect sentences. Depending on where you're from, people say all sorts of things that don't make sense in the literary world. Ain't is common where I live, and we all know that isn't really a word.
I'm not saying to pepper your dialogue with slang, but a few choice words here and there will make the dialogue feel so much more natural. Whatever you do, don't feel the need to be technically correct. Your characters can say things that would make you cringe if you were to write them in any other way. People are expressive and excitable. We humans ask so many questions in a row and tend to not wait for the answers. We exclaim a lot too. (Though exclamation marks embarrass some people - me included to be honest. I only ever use them in dialogue.)
Once you've played around a bit, you can make each character's 'voice' distinctive. Some will be sarcastic. Some talk a lot and always want the last word. Some only speak when they have something important to say. Some will exclaim a lot and be more excitable than others. It's so useful to write dialogue in such a way that the reader immediately knows who's speaking. It can take away the pain of having to type 'said' all the time.
Before you get too carried away, make sure all your dialogue has a point. Sometimes I go off and have a fantastic conversation between some of my characters, only to come back and cut the entire thing because it didn't go anywhere. Chatting in real life doesn't usually go anywhere, but in your story, it must have some sort of reason to be present.
Dialogue is so important. It plunges your reader into your world and also gives you a way into secondary characters' heads. The things they say and how they say them are so important for getting to know them better. If you're lacking dialogue, you're also lacking heart.
The only other tip I have is to listen. Whenever you're having a conversation, listen to its flow. When you're in a queue, listen to the people chatting around you. Immerse yourself in the art of human conversation and make note of how sometimes (in fact most of the time) it's not what people are saying, it's how they're saying it, and how they're standing/looking at you. Sometimes a picture really does paint a thousand words.
So go, newly inspired chatterboxes! Go and irritate everyone in your search for perfect natural dialogue.