My most successful big event I have done for practicing is having students earn music money for each minute they spend practicing. (I did a 10 minute minimum to earn the money because I didn't want to mess with one dollar bills) I was able to immediately hear a difference in my orchestra when I started this event and my students are already requesting that we do it again!
Here is where I downloaded the temple for my money:
I then used Publisher to make my money look a little more musical:
This was then printed on green paper and I had my TA cut them all out. (It was a lot, but she had time.)
I gave students 3 weeks to earn their practice money. As students came to class each day, they picked up the correct amount of money depending on their practice. They wrote their names on the back and put them in a special manilla envelope.
At the end of the 3 weeks, I had my TA sort all of the money into piles and paper clip together the money that was turned in by each student. I then held an orchestra auction and allowed students to bid on items and spend their money. We did this right after our last concert and it made for a great celebration. I auctioned off things like candy, dollar store items, bumper stickers, pencils, certificate for extra credit, certificate for a free pass on one playing test.......