Creating dialogue for your characters seems like a daunting process, but in reality is an enriching process for building your skills as a writer. For most, dialogue is two-dimensional. My friend, who is an accomplished artist, illustrated this point to me over coffee once. If I look at a crowded restaurant, what I see will be much different than what he sees. My eyes will be blind to the depth, the color, the contours in shape and tone that he will recognize instantly. Just like art, people that excel at the craft of writing see dialogue as a way of giving depth, shape, form, and contour to a character when most take it for granted.
One of the best pieces of dialogue advice I ever heard was from Kurt Vonnegut who said, "Every sentence must do one of two things: reveal character or advance the action."
I believe both are possible.
The first step to take is to write out the interchange between the characters that you are planning to use. From here, read over the dialogue and tailor it so that your reader can grasp and understand who the characters are without any sensory descriptions. People rely far too much on imagery to substantiate their characters. It's certainly important, but dialogue is far more memorable in my opinion. I mostly say this because people don't quote the descriptions of Westley from The Princess Bride, but the things he says. Those endearing things are what propel the character into memory.
Another good tip is asking after every line of dialogue you write, "would so-and-so say this?" Not only does this make your writing process more cerebral, but it helps you critically think and break down what the core of your character is. If your character is a vagrant who courts prostitutes and random acts of violence, then he's going to swear, be crude, and welcome conflict. Even if you are Christian (like me) the character doesn't represent your morals and ideals, so he/she shouldn't be your mouthpiece.
The last piece of advice I have is pick your unique style of dialogue presentation and stick with it for the sake of consistency. If your character speaks in an accent, he must carry it the full length of the novel. If your character stutters, he must carry the stutter the full length of the novel. If your character speaks in broken disjointed thoughts, or maintains a mystical presence, then font, punctuation, and sentence syntax must reflect this always. Neil Gaiman is king of this and I encourage all of you to consult his corpus to see what I mean. Especially his Death character in Good Omens.
Always remember that rules are made to be broken, but they need to be broken intelligently and thoughtfully.