I have been using/experimenting (I'm by no means an expert yet) with WBT for the past year. The most effective motivator, thus far, for my kids (9th grade) has been more/less homework. They HATE it when I "add" to their workload, even if it's just 5 additional problems. The key, of course, is to decide, AHEAD OF TIME, where you PLAN for the scoreboard to end up. That way, you KNOW how to assign the homework. (e.g. my plan for THEM winning: Problems 1-10 or my plan for them losing: Problems 1-5, and then at the end "Oh dear, look like you guys lost today, so you ALSO have to do 6-10!)
They also, believe it or not, do work for "Mind Soccer" time at the end of class (though I have to be careful not to overuse it, as with all things) I always have a warmup and "Exit Ticket," but will "let" them play for Mind Soccer in lieu of the Exit Ticket (last 3 minutes of class).
When their interest in Mind Soccer started to wear off, I upped the ante by offering "merit points" (a schoolwide incentive we have) to the winning team. (20 merit points gets them a spot on the Bingo Board in the cafeteria - when filled, the school uses bingo balls to award nice prizes).
(PS Boys vs. Girls can work, but with one class, I only had about 6 boys and 20 girls, so it wasn't really fair to do it that way! Instead I divided them up one side (east) vs. the other (west).
I also tried using "Girls" vs "boys" on the ScoreBoard, but found it was difficult to "administer" the rewards/consequences (can't give one group extra homework and not the other). So, later in the year, I made it a weekly tally - whichever group was "ahead" by the end of the week would get a homework pass (printed by me on pink paper and initialed with a silver sharpie to prevent counterfeiting) good through the end of the month. Our school gives Friday Detentions (2 hours) to any student who has missed 3 or more homeworks, so this was a VERY VALUABLE thing to have for that third missing assignment....
And NO, I do NOT give "FREE TIME" or TALKING TIME. That's just a pandora's box with my kids. I haven't really experimented with music yet, but I do a number of labs (I teach science) and I am considering allowing them to play for "music DURING labs."
My biggest challenge next year is to master the "Teach-OK." I think I'm still not moving quickly enough through that whole cycle and there's still too much transition time where my kids start getting off-task..... I'm going to spend some time this summer planning my first unit using that 5-step template we learned in Louisiana.
In the end, I agree that you have to figure out what motivates your class, and even then, each class may be different. I had one class that LOVED merit points, and another that couldn't care less (but HATED homework!)
Hope this helps.
- Jen