Keep my fingers crossed

It refers to crossing middle finger over the index finger for hoping good luck or thing will happen in the way you want it to. It is similar to the Chinese slang of "Qiu Shen Bai Fo" 求神拜佛 (beg the Buddha by keep both hands closed together and shake a bit); i.e. 求神拜佛, 千祈唔好有事哎.

Example:
I'm keeping my fingers crossed that we can catch the flight.

He keeps his fingers crossed hoping everything will turn out okay.

"Keep your fingers crossed, everyone, Katie may win a house as long as she picks the box with the key inside." the MC said to the audiences.