Get over feeling pushy. The one single factor that keeps a lot of people from getting paid what they're worth is wanting to be "nice" and not self-advocate. Other than that, it's a multi-step process.
The first thing you must do is set a reasonable salary target. What you don't want to do is make up a number based on what you'd like to make. What you should do is research what others in your position are making, and base your projection on actual market data.
Second, create a list of accomplishments that you have personally achieved since your last raise. Be specific in pointing out anything that has made or saved the company money.
When you have your goal and reasons why, wait for your boss to acknowledge something positive you did or compliment you. By doing this, you wait until you know you are in a positive state in their mind. That's when you request a private meeting.
In the meeting, use positive, confident, powerful body language. Point out your accomplishments and then ask for a specific raise, but do so in terms of a percentage. If the answer is yes, you've won. If the answer is no, ask what you need to do to make it happen so that you have a door open for round two.