Oddly for me it comes when I get less hung up on concentrating. If I sit with an attitude of "I have GOT TO concentrate now" my mind tends to go "no thanks" and I end up with little to no consistent concentration. If I sit with an attitude of "sometimes I will lose my meditation object, sometimes I won't. It's fine. Meditation doesn't always go well." I tend to be less hard on myself for losing concentration. Eventually distractions occur but take a backseat before sometimes vanishing entirely.
And if I'm really distracted I just let it be and try to watch the storm. I think an overly strict on yourself attitude to concentration is a big hindrance to it.
"For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring."