I Never Follow My Own Advice...
You have to get the backbone to take things to the cusp of actually leaving. Of course, before you do this, try to feel out how much they actually NEED you, versus the amount of work out there if you DID leave (even at a slight pay cut) versus the amount of qualified people that are looking to take your job...
Otherwise, employers know they have you by the short and curlies. They WILL take advantage of this, even if they have a 'good' relationship with you. Money is money, after all.
I had a friend that decided to move West, so her boyfriend, who made ~$35k went in to tell his boss he had to leave. To cut the story short, 45 minutes and several offers and impassioned pleas later, the boyfriend told the boss to go screw himself after the final offer of $50k. "Even if I COULD stay," he said, "I'd know that you didn't respect me for not offering me anything close to that salary over the past few years!"
