Go to the option screen where you can set your credit number, press
triangle+circle+square+X at the same time, you will get FREEPLAY.
Siu-kwong Yau
This only works on the Japanese version:
I found out that every times I hit the 
select button after I had died(at the count down)
it would always keep me with full credits for 
continues.
- Kumpol Trivisvavet