1. When I was a child we had a tradition of "jumping into New Year", which basically meant we jumped ahead as far as we could as soon as the clock struck 12.
2. When I was a teenager, as soon as clock started striking 12, we quickly wrote our wishes on the paper, burnt it, threw the remaining to the champagne and drank it. If we were in time to do everything before the 12th strike, it meant the wishes will come true.
3. In Spain there is a tradition to make a wish and with each clock strike eat 12 grapes (1 grape per each strike). If you eat all 12, the wish will come true.