Just start with a forum competition: big announce for all forum including locals, make Google form with price prediction at the end of the week and username > Google spreadsheets. Prediction +/- 5% of actual price gives 3 points, 10% – 2 points, 15% – 1 point, less than 1% is 5 points. At the end of the month 50% highest score owners goes in the next round (month). Top 10 receives a traders rank with 10-9-8-7-6-5-4-3-2-1 points system.