You have to do this in two steps.
First, you must make a case for your present value. In other words, you need to tell them why and how you are valuable - you meet project deadlines on time, you take initiative, you've come up with innovative solutions to problems, etc. Make sure you provide examples.
Second, you must tell them about your future value with the company. Tell them about your ambitions in your current position
. Examples: 1) You intend to take further training (possibly on your own dime) so that you are more effective in your position, or can take on more responsibilities; 2) You perceive additional responsibilities that you would like to take on; or 3) You've identified a specific project that you would like to initiate and complete to the benefit of the company. Again, be specific.
If they agree or seem interested, you then have your foot in the door. Most of the time, they know what you're aiming for and often times will initiate the pay increase discussion themselves.
Just remember that if you're dealing with a rational HR
department, they will look at it as an economic equation...what value do you add to the company and are you paid equitably...by adding to your responsibilities can they justify paying you more because they don't have to hire someone else...or, perhaps, you're simply so valuable that they want to make sure to keep you.
Anyway, take a rational approach. They'll respect you if you make your case and cite specifics.