Are you sure the sound is from the front wheel? If so, squeeze them to see if they have movement just as others suggested. If there is movement tighten the loose spokes 1/4 turn at a time. I also suggest putting a little silicon oil at the point the spokes cross. If you are not certain about the noise coming from the front wheel, I suggest tightening your crank arms because they can come loose and often cause a clicking sound too.