How do I make the platform side of a Shimano PD-A530 multi-purpose SPD pedal less "slippery"? The lock side is great, however, shoes does not stay on the platform side. Your leg always slip out from the pedals during pedaling. Any solution to improve it?
Some people have modded the pedals to add set-screws which provide better grip.  Typically this involves drilling a hole, tapping it for threads, and adding a set screw of the desired length.

For example, here's an a530 with 2x set screws added: