Challenging a sibling or cousin to a wishbone breaking contest is tradition for many families, and thanks to some important research recently conducted by university scientists, we now have some actual strategies to help ensure you always break off the biggest piece and *have your wish come true. (*Wish may not come true.)
The most obvious strategy is to always try and grab whichever side of the wishbone looks thicker, because it will be less likely to snap first. But choking up on your side of the bone can help improve your chances too, as it helps to reinforce your side -- although that could lead to accusations of cheating.
The most useful tip is to try and let the other person do most of the actual pulling. The more their side of the bone has to move, the more it will bend and deform, increasing stresses that cause points of weakness. Ninety-nice per cent of the time if you can remain stationary while the other person does all the pulling, you'll come out on top.