It's something you learn by degrees. It'll be very hard to feel like you're in the right state at first, but with time, you'll find yourself becoming totally calm after just a few minutes.
I recommend doing it outside, in your backyard if you have one. Don't resist sound distractions. What I do, is when I hear cars and birds and whatnot, I don't picture the source of the sound. I just picture sound vibrations reaching my ears.
Keep that in mind, and don't think about anything other than breathing. Breathe slowly and calmly, and try to breathe in through your stomach, like how you see babies breathe. If you have distracting thoughts, don't actively try to shut them out. Just don't hold on to them. You'll find a thought will flicker and then just disappear.
Do this a few times a week, and after a while you should notice that as soon as you sit down and take a few deep breaths, you'll be calm. After that you can start adding things, like visualizations, humming, music. Remember though - you're not meditating to reach some deep insight. The only purpose is to bring yourself one hundred percent into the moment - for just a few minutes, you need to stop thinking about the future and the past.