My own personal opinion, so feel free to disagree:
I've tried that and failed quite a few times too. I think Asians have a different way of thinking actually and more often than not when it comes to numbers or whatever, the way they think is vastly different from Americans or Europeans (but that's another can of worms I'm trying to "research" on and find out).
Anyway, what I do is, if it's in a group setting, and say the guy doesn't give the number I want, I nonchalantly turn to the person next to him and ask the same question. And do that again with one or two more people.
At that point, they should have varied answers since they would instinctively avoid the numbers already picked by the other people, or two of them may have the same number. Whatever the case, I just go on and say something like, "Now you see each human being is unique in the way they think. I've asked each one of you the same question, and you all gave different answers. However, it
is possible for one mind to be in tune with another, and share its thoughts or brain pattern... blah blah blah". Then move on to another trick. I usually do another number trick to keep with the "theme".
That way it becomes a non-effect. They do not think you have failed anything because you didn't announce you were doing anything. For this reason I feel it may not be good to start by saying that you have a slip of paper with a number in your pocket and then reveal it's the same number as the one they have chosen. So the initial question is phrased somewhat vaguely, "Hey... Let's try something. I like you to quickly, quickly now, think of a number from 10-50, with different digits, and each digit must be an odd number. Quickly now. You got your number? Was it 37? No? It wasn't 37? *turn to a few other guys, ask the same thing* ... Now you see, when I was first asked this question, I picked the number 37, but here you all picked different numbers... blah blah."
Yea... Just two-cents from a newbie.
